JP2012118429A - Image forming method - Google Patents

Abstract

There is provided a developing device having a configuration capable of easily removing a developer from a developer carrying member and reliably collecting the developer over a long period of time.
A developer carrier for supplying a two-component developer containing toner and a carrier to an electrostatic latent image formed on an image carrier, the developer carrier having an inside thereof, In an image forming method using a developing device in which a rotatable magnetic field generating means having a magnetic pole for causing a developer to stand up and transport is arranged, the carrier includes a core material and a coating film covering the core material. And the surface is covered with the coating film, the coating film contains a binder resin and particles, and the average height difference is 0.05 μm or more and 2.0 μm or less. An image forming method using a carrier, wherein a ratio of an average particle diameter of the particles to an average film thickness is 0.01 or more and 1.0 or less.
[Selection] Figure 9

Description

  The present invention relates to an improved developing apparatus and developing method, and a developer and an image forming method therefor, and in particular, a specific combination of a two-component developer including a toner and an improved carrier and a specific developing mechanism. The present invention relates to an image forming method to be used.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a printing machine, an electrostatic latent image formed on a photosensitive member as a latent image carrier is subjected to visible image processing by a developing device, and the visible image is converted into a sheet. A recording output can be obtained by transferring to the above.

  As a developer used for development, there is a two-component developer obtained by mixing a toner and a carrier in addition to a one-component developer containing only magnetic or non-magnetic toner.

  The two-component developer is composed of a toner and a carrier that carries the toner, and the toner can be electrostatically attracted to the electrostatic latent image on the photosensitive member by charging the toner by a frictional charging effect that occurs during stirring and mixing. It is said.

  In the developing device, a developing sleeve as a developer carrying member for supplying developer toward the electrostatic latent image on the photosensitive member by causing the developer to rise on the peripheral surface by magnetic force, and agitating and mixing the developing sleeve A configuration including a stirring member such as a screw auger for supplying a developer is known. The developer carried on the developing sleeve is supplied to the electrostatic latent image on the photosensitive member after a carrying amount (layer thickness) is defined by a regulating member such as a doctor blade.

  A configuration of a developing device using a two-component developer is shown in FIG. 17 (for example, Patent Document 1).

  In the configuration shown in FIG. 17, a developer supplying auger (401) is disposed below a position where a developing sleeve (5) as a developer carrying member is disposed, and the developer supplying auger (401) in the horizontal direction. A stirring auger (402) parallel to the axis of Each of the augers (401) and (402) for supply and stirring is in communication with the space where these augers are arranged at the axial end.

  In the configuration shown in FIG. 17, the developer is circulated between the spaces where the augers are arranged by transferring the developer in the direction in which the screw augers oppose each other. Thus, the developer is pumped from the supply auger (401) to the developing sleeve (5), and the developer carried on the developing sleeve (5) after development is collected.

  As a configuration for supplying and collecting the developer described above, a developing main pole and a developing device in which a magnetic brush is raised in the developing sleeve (5) in the circumferential direction so as to face the developing sleeve (5). There are provided a magnetic pole for transporting the developer on the sleeve and a peeling magnetic pole capable of forming a repulsive magnetic field for peeling the developer from the peripheral surface of the sleeve after development. Specifically, a 7-pole magnet is used.

The developer peeled off and collected from the peripheral surface of the developing sleeve (5) by the repulsive magnetic pole once passes through the conveying path (401P) as indicated by the one-dot chain line arrow (F1). However, it is again pumped up by the conveying magnetic pole and supplied to the peripheral surface of the developing sleeve (5).
As a result, the developer is conveyed in the axial direction of the auger while circulating between the supply conveyance path and the collection conveyance path existing at the same position, and while facing the magnetic pole on the developing sleeve side many times in the process. Moving. The developer is in a spiked state when facing the magnetic pole, and when separated from the magnetic pole, the spikes collapse and condense, and the frictional contact between the carrier and the toner is performed, and the toner is triboelectrically charged. Is called.

  The developer in which the frictional contact due to the rising state and the rising state collapses and condenses is repeated, for example, in the axial direction of the auger. Therefore, if the toner consumption increases in the conveying process in that direction, the developer is conveyed. The toner density on the downstream side in the direction decreases.

  For example, when developing an image with a large image area, the toner consumption in the auger axial direction is likely to be consumed in large quantities on the supply side, and the developer is contained on the downstream side in the transport direction. The amount of toner is reduced. For this reason, a uniform toner density may not be maintained in the axial direction of the developing sleeve. Insufficient toner density leads to a decrease in image quality.

  The above-described problems are caused by the common use of the developer supply conveyance path and the recovery conveyance path. In other words, the collected developer is insufficient in toner, and if such developer is conveyed again to the supply conveyance path, the carrier content ratio in the supplied developer becomes high, The ratio of the carrier and the toner in the supplied developer is different from the predetermined ratio.

Accordingly, a configuration is proposed in which a part of the configuration shown in FIG. 17 is changed so that the developer supply and recovery paths are distinguished from each other so that the collected developer is not mixed in the supply and transfer paths. (For example, Patent Document 1).

  FIG. 18 shows a main part of the developing device disclosed in Patent Document 1, in which the housing of the developing device (4) is partitioned in the vertical direction by a partition wall (403). A stirring chamber (401P) for storing the first auger (401), a second auger (209), and a stirring chamber (402P) for storing the third auger (402) are provided.

  On the other hand, as disclosed in Patent Document 1, there is a configuration disclosed in Patent Document 2 as another example of a configuration in which the stirring chamber that houses the auger is partitioned by a partition wall.

  FIG. 19 is a diagram showing the configuration disclosed in Patent Document 2, in which a supply auger is provided in the housing of the developing device (4) for supplying developer to the developing sleeve (5). (401) and a developer agitating auger (402), a collecting auger (404) for collecting the developer on the developing sleeve (5) that has passed through the developing region is provided, and a supply auger (401) is provided. The supply conveyance path (401P) located and the collection conveyance path (404P) where the collection auger (404) is located are partitioned by a partition wall (405), and the agitation conveyance path (402P) where the agitation auger (402) is located. ) And the collection transport path (404P) are partitioned by a partition wall (406).

In the configuration disclosed in Patent Document 1, since the collected developer is conveyed in the axial direction by the auger for stirring (402) and is conveyed as it is toward the auger for supply (401), a new toner is obtained. Even when the toner is replenished, stirring by the auger (402) for stirring tends to be insufficient, and there is a possibility that the image density is uneven or the density is lowered due to insufficient charging of the toner.
This is particularly noticeable when forming an image with a high printing rate in which the toner concentration of the collected developer tends to decrease.

  On the other hand, in the configuration disclosed in Patent Document 2, the developer recovered from the developing sleeve is transported to the recovery transport path (404P) and is not mixed into the supply transport path (401P). The collected developer does not enter the agitating conveyance path (402P) as it is, but is agitated and conveyed toward the supplying conveyance path (401P). Can be expected to be resolved.

  However, the configuration of the developing sleeve, which is a developer carrier used in the configuration disclosed in these patent documents, has the following problems.

  The developing sleeve disclosed in each patent document is provided with a magnetic pole for forming a magnetic brush, that is, a developer to make it stand up. The number of magnetic poles is shown in Patent Document 1 as shown in the figure. Although it is made of five poles and is not shown in Patent Document 2, it is described that the developer moves toward a collecting screw that collects the developed developer that has passed through the developing section. In the case shown in FIG. 18 or in the same manner as in Patent Document 1, it can be expected that the number is about 5 or 7.

  On the other hand, in the configuration disclosed in Patent Document 1, unlike the case shown in FIG. 17, the supply conveyance path and the collection conveyance path are not common and are independent, The developer cannot be circulated between the supply / recovery conveyance path.

  For this reason, the collected developer is collected in a state where the number of times of passing through the magnetic pole is only 5 to 7 times, and the frictional contact at the time of repeated rise and fall of the rise is caused. An extremely low state is obtained. As a result, the frictional charging caused by the frictional contact becomes insufficient, and a long time is required for charging the toner, which causes problems such as the durability and chargeability of the developer, particularly the carrier.

  In the configuration disclosed in Patent Document 2, since the agitation conveyance path is provided independently, it is possible to improve the agitation efficiency for the collected developer. Since the charge amount of the toner tends to be lost when the toner is left as it is, the adhesion to the carrier is reduced and the toner tends to be scattered. As a result, there is a possibility of causing contamination in the apparatus.

  By the way, in this type of developing device, after the developer remaining on the developing sleeve (5) that has passed through the developing region is recovered, a new developer is supplied to the developer sleeve (5). It is necessary to keep the concentration of developer carried constant.

  However, if the developer cannot be recovered satisfactorily from the developing sleeve (5) that has passed through the developing region, the concentration of the developer carried on the developing sleeve changes and an image having a predetermined density cannot be obtained. . In other words, the developer concentration remaining on the developing sleeve (5) is lowered due to the consumption of the toner, and if the developer is used as it is, the concentration is lowered or a ghost image is obtained. A malfunction occurs.

  SUMMARY OF THE INVENTION In view of the above problems in the conventional developing apparatus, the present invention provides an image forming method having a configuration capable of easily removing a developer from a developer carrying member and reliably collecting the developer. There is to do.

In order to achieve this object, the present invention has the following configuration.
(1) A developer carrier for supplying a two-component developer containing toner and carrier to the electrostatic latent image formed on the image carrier is provided. In the image forming method using a developing device in which a rotatable magnetic field generating means having a magnetic pole for causing the agent to be spiked and transported is disposed, the carrier has a core material and a coating film that covers the core material. The surface is covered with the coating film, the coating film contains a binder resin and particles, and the average height difference is 0.05 μm or more and 2.0 μm or less. The image forming method, wherein the ratio of the average particle diameter of the particles to the film thickness is 0.01 or more and 1.0 or less.
(2) The developing device characterized in that the magnetic field generating means is arranged with its cross-sectional center decentered in a direction approaching the image carrier relative to the cross-sectional center of the developer carrier. The image forming method according to item (1), wherein:
(3) Due to the eccentricity of the developing device, a part of the magnetic field generating means is placed in a gap space existing between the side opposite to the image carrier in the magnetic field generator and the inside of the developer carrier. The image forming method according to item (2), wherein a magnetic shielding member capable of being covered is disposed.
(4) The ratio of the average particle diameter of the particles to the average film thickness of the carrier coating film is 0.01 or more and 0.7 or less, the item (1) or the item (2), The image forming method described in 1.
(5) The image according to any one of (1) to (4), wherein the particles in the carrier coating film contain alumina, silica, carbon black, or titanium oxide. Forming method.
(6) The volume specific resistance of the carrier is 1 × 10 ⁹ Ω · cm or more and 1 × 10 ¹⁴ cm or less, according to any one of (1) to (5), Image forming method.
(7) The volume resistivity of the carrier is 1 × 10 ⁹ Ω · cm or more and 1 × 10 ¹² cm or less, according to any one of (1) to (6), Image forming method.
(8) The carrier according to any one of (1) to (7), wherein the carrier has a magnetization in a magnetic field of 1 kOe of 40 Am ² / kg or more and 90 Am ² / kg or less. Image forming method.
(9) The carrier according to any one of (1) to (8), wherein the carrier has a magnetization in a magnetic field of 1 kOe of 60 Am ² / kg or more and 90 Am ² / kg or less. Image forming method.
(10) The ratio of the weight of the particles to the sum of the weight of the binder resin and the particles of the carrier coating film is 10% or more and 80% or less. (9) The image forming method according to any one of items.
(11) The ratio of the weight of the particles to the sum of the weight of the binder resin and the particles of the carrier coating film is 40% or more and 70% or less. (10) The image forming method according to any one of items.
(12) In the items (1) to (11), the magnetic field generating means of the developing device is provided with even-numbered magnetic poles along the rotation direction. The image forming method according to any one of the above.
(13) The magnetic shielding member is provided with a shielding angle larger than an angle between magnetic poles provided in the magnetic field generating means. The image forming method according to any one of items 1) to 3).
(14) The magnetic shielding member is characterized in that the edge along the rotation direction of the magnetic field generating means is not parallel to the magnetic pole provided on the magnetic field generating means. Item 15. The image forming method according to any one of Items (13) to (13).
(15) The magnetic shield member is configured by arranging a plurality of magnetic poles along the longitudinal direction of the magnetic field generating means. The image forming method described in 1.
(16) The plurality of magnetic poles provided on the magnetic shielding member have a polarity capable of suppressing flexural vibration along the longitudinal direction of the shielding member due to the magnetic force from the magnetic pole provided on the magnetic field generating means. The image forming method according to any one of (1) to (15), wherein the image forming method is set.
(17) The magnetic shielding member may be formed by attaching a magnetic sheet having a plurality of magnetic poles to any one of the items (1) to (16). The image forming method described.
(18) The magnetic shielding member is a plate-like member, and the plate-like member is configured to have a different thickness in the longitudinal direction, wherein the items (1) to (17) are characterized. The image forming method according to any one of the above.
(19) The magnetic shielding member is located in the developer carrying body in the gap space between the surface of the magnetic field generating means opposite to the side facing the image carrier and the inner surface of the developer carrying body than the magnetic field generating means. The image forming method according to any one of (1) to (18), wherein the image forming method is arranged close to a surface side.
(20) The magnetic field generating means is rotatable in the same direction or in a relative direction with respect to the developer carrying member, and when rotating in the same direction, a relative speed difference is set to rotate. The image forming method according to any one of (1) to (19).
(21) A developing device comprising a developer carrier for supplying a two-component developer containing toner and carrier to the electrostatic latent image formed on the image carrier, the developer carrier In the inside, a rotatable magnetic field generating means provided with a magnetic pole for causing the developer to stand up and transported is disposed, and the carrier has a core material and a coating film covering the core material, The surface is covered with the coating film, the coating film contains a binder resin and particles, the average height difference is 0.05 μm or more and 2.0 μm or less, and the average film thickness of the coating film The ratio of the average particle diameter of the particles to the developing device is 0.01 or more and 1.0 or less.
(22) The developing device characterized in that the magnetic field generating means is arranged with its own cross-sectional center decentered in a direction approaching the image carrier relative to the cross-sectional center of the developer carrier. The developing device according to item (21), wherein:
(23) Due to the eccentricity, a gap space existing between the side opposite to the image carrier in the magnetic field generator and the inside of the developer carrier can partially cover the magnetic field generator. The developing device according to item (22), wherein a magnetic shielding member is disposed.
(24) The magnetic field generating means is provided with even-numbered magnetic poles arranged in the direction of rotation thereof, according to any one of (21) to (23). Development device.
(25) Items (21) to (24), wherein the magnetic shielding member is provided with a shielding angle larger than an angle between magnetic poles provided in the magnetic field generating means. The developing device according to any one of the items).
(26) The magnetic shield member is characterized in that an end along the rotation direction of the magnetic field generating means is not parallel to the magnetic pole provided on the magnetic field generating means. The developing device according to any one of Items 25 to 25.
(27) The magnetic shielding member is configured by arranging a plurality of magnetic poles along the longitudinal direction of the magnetic field generating means, and any one of the items (23) to (26), The developing device according to 1.
(28) The plurality of magnetic poles provided in the magnetic shielding member have a polarity capable of suppressing flexural vibration along the longitudinal direction of the shielding member due to the magnetic force from the magnetic pole provided in the magnetic field generating means. The developing device according to item (27), wherein the developing device is set.
(29) The developing according to any one of (23) to (28), wherein a magnetic sheet having a plurality of magnetic poles is attached to the magnetic shielding member. apparatus.
(30) Item (23) to Item (29), wherein the magnetic shielding member is a plate-like member, and the plate-like member has a different thickness in the longitudinal direction. The developing device according to any one of the above.
(31) The magnetic shielding member is disposed in the developer carrying body in the gap space between the surface of the magnetic field generating means opposite to the side biased to the image carrier and the inner surface of the developer carrying body than the magnetic field generating means. The developing device according to any one of (23) to (30), wherein the developing device is arranged close to the surface side.
(32) The magnetic field generating means is rotatable in the same direction or in a relative direction with respect to the developer carrying member, and when rotating in the same direction, a relative speed difference is set to rotate. (23) The developing device according to any one of (31) to (31).
(33) An image forming apparatus comprising a process cartridge in which at least the developing device according to any one of the items (21) to (32) and the image carrier are collectively accommodated.
(34) A developer carrying body for supplying a two-component developer to the electrostatic latent image formed on the image carrying body is provided, and the developer is spiked inside the developer carrying body. A two-component developer mounted on a developing device in which a rotatable magnetic field generating means having a magnetic pole to be conveyed is disposed, and includes a toner and a carrier, and the carrier includes a core material and the core material. The coating film has a coating film, the surface is covered with the coating film, the coating film contains a binder resin and particles, and the average height difference is 0.05 μm or more and 2.0 μm or less. The two-component developer, wherein the ratio of the average particle diameter of the particles to the average film thickness of the coating film is 0.01 or more and 1.0 or less.
(35) The ratio of the average particle diameter of the particles to the average film thickness of the carrier coating film is 0.01 or more and 0.7 or less, wherein the two-component system according to (34) above Developer.
(36) The two-component development according to (34) or (35), wherein the particles in the carrier coating film contain alumina, silica, carbon black, or titanium oxide. Agent.
(37) The volume specific resistance of the carrier is 1 × 10 ⁹ Ω · cm or more and 1 × 10 ¹⁴ cm or less, according to any one of (34) to (36), Two-component developer.
(38) The volume resistivity of the carrier is 1 × 10 ⁹ Ω · cm or more and 1 × 10 ¹² cm or less, according to any one of (34) to (37), Two-component developer.
(39) The carrier according to any one of (34) to (38), wherein the carrier has a magnetization in a magnetic field of 1 kOe of 40 Am ² / kg or more and 90 Am ² / kg or less. Two-component developer.
(40) The carrier according to any one of (34) to (39), wherein the carrier has a magnetization in a magnetic field of 1 kOe of 60 Am ² / kg or more and 90 Am ² / kg or less. Two-component developer.
(41) The ratio of the weight of the particles to the sum of the weight of the binder resin and the particles of the carrier coating film is 10% or more and 80% or less. The two-component developer according to any one of (40).
(42) The ratio of the weight of the particles to the sum of the weight of the binder resin and the particles of the carrier coating film is 40% or more and 70% or less. The two-component developer according to any one of (41).

  According to the present invention, the magnetic field generating means is provided so as to be rotatable in the developer carrying body and decentered in a direction approaching the latent image carrying body with respect to the center of the cross section of the developer carrying body. Therefore, it is possible to facilitate the peeling of the developer by making it difficult to exert a magnetic force on the surface of the image carrier, and to increase the agitation as much as possible to satisfy the charging characteristics of the developer toner. A developing device that increases the stress) is coated with a two-component developer, ie, a core material, which includes the toner of the developing device and a specific carrier and has excellent agitation durability and excellent toner's sustained chargeability, and the core material. The surface is covered with the coating film, the coating film contains a binder resin and particles, and the average height difference is 0.05 μm or more and 2.0 μm or less, The ratio of the average particle diameter of the particles to the average film thickness of the coating film is: By applying a two-component developer containing a carrier of 0.01 or more and 1.0 or less, it is possible to stir over a long period of time and provide an image with stable image quality without image density unevenness. An extremely excellent effect that it can be achieved.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus in which a developing device according to an embodiment of the present invention is used. FIG. 2 is a schematic diagram for explaining the configuration and operation of a developing device used in the image forming apparatus shown in FIG. 1. FIG. 3 is a perspective view illustrating an appearance of a main part of the developing device illustrated in FIG. 2. FIG. 3 is a schematic diagram for explaining the flow of developer in the developing device shown in FIG. 2. FIG. 4 is a schematic diagram illustrating a cross section viewed from a direction indicated by an arrow J in FIG. 3. FIG. 5 is a schematic diagram for explaining another example of the developer flow in the developing device shown in FIG. 2. FIG. 3 is a perspective view of relevant parts for explaining the configuration of a toner replenishing unit in the developing device shown in FIG. 2. FIG. 4 is a perspective view of main parts showing a state in which some members in the developing device shown in FIG. 3 are removed. FIG. 3 is a schematic side view for explaining a characteristic part in the developing device shown in FIG. 2. It is a perspective view for demonstrating the structure of the developer carrier used for the characteristic part shown in FIG. FIG. 10 is a waist cross-sectional view for explaining a support structure of the developer carrying member shown in FIG. 9 and a magnetic field generating unit included in the developer carrying member. It is an effect | action figure which shows the opposing relationship of the magnetic shielding member and magnetic field generation | occurrence | production means for demonstrating the malfunction by the structure shown to Table 1,2. It is a perspective view equivalent to the Example of Table 1, 2 for demonstrating the structure which eliminated the malfunction by the magnetic shielding member shown in Table 1, Table 2. FIG. FIG. 14 is a perspective view corresponding to the embodiment of Table 1 showing a modification of the main part of the magnetic shielding member shown in FIG. 13. It is a schematic diagram for demonstrating the opposing relationship of the magnetic shielding member and magnetic generation | occurrence | production means for demonstrating another example for eliminating the malfunction which arises by the structure shown to Table 1,2. It is a schematic diagram for demonstrating the prior art example of the developer supply mechanism in a developing device. It is a schematic diagram for demonstrating one structure conventionally known in order to eliminate the malfunction in the prior art example shown in FIG. It is a schematic diagram for demonstrating an example different from FIG. It is a schematic diagram for demonstrating the structure of the reference example using the magnetic shielding member shown in FIG. It is a figure which shows another example of the conventional developing device. It is a figure which shows a powder resistance measuring apparatus.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 shows a developing device according to the present invention, an image device using the same, and an image forming method. The image forming device shown in FIG. 1 is a tandem full-color printer. However, the present invention is not limited to this. It can also be applied to copying machines, facsimile machines, and the like.

FIG. 1 is a schematic configuration diagram of a full-color printer (hereinafter referred to as a copying machine for convenience) 500 according to the present embodiment.
The copier (500) includes a printer unit (100), a paper feeding device (200) on which the printer unit (100) is mounted, a scanner (300) fixed on the printer unit (100), and the like. An automatic document feeder (400) is fixed on the scanner (300).

  The printer unit (100) includes four process cartridges (18Y, 18M, 18C, 18K) for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K). An image forming unit (20) is provided.

  The symbols Y, M, C, and K added after the numerals indicate the members for yellow, magenta, cyan, and black (the same applies hereinafter). In addition to the process cartridges (18Y, 18M, 18C, 18K), an optical writing unit (21), an intermediate transfer unit (17), a secondary transfer device (22), a registration roller pair (49), a belt fixing type A fixing device (25) and the like are provided.

The optical writing unit (21) has a light source, a polygon mirror, an f-θ lens, a reflection mirror, etc. (not shown), and irradiates the surface of the photoconductor described later with laser light based on image data.
The process cartridge (18Y, 18M, 18C, 18K) includes a drum-shaped photoreceptor (1), a charger, a developing device (4), a drum cleaning device, a static eliminator, and the like.

The yellow process cartridge (18) will be described below.
The surface of the photoreceptor (1Y) is uniformly charged by a charger as charging means.
The surface of the photoreceptor (1Y) that has been subjected to the charging process is irradiated with laser light that has been modulated and deflected by the optical writing unit (21). Thereby, the electric potential of the surface of the photoreceptor (1Y) of the irradiation part (exposure part) is attenuated. Due to the attenuation of the surface potential, an electrostatic latent image for Y is formed on the surface of the photoreceptor (1Y). The formed electrostatic latent image for Y is developed by a developing device (4Y) as developing means to become a Y toner image.

  The Y toner image formed on the Y photoconductor (1Y) is primarily transferred to an intermediate transfer belt (110) described later. After the primary transfer, the surface of the photoreceptor (1Y) is cleaned of residual toner by a drum cleaning device.

  In the Y process cartridge (18Y), the photoconductor (1Y) cleaned by the drum cleaning device is discharged by the charge eliminator. Then, it is uniformly charged by the charger and returns to the initial state. The series of processes as described above is the same for the other process cartridges (18M, 18C, 18K).

Next, the intermediate transfer unit (17) will be described.
The intermediate transfer unit (17) includes an intermediate transfer belt (110) and a belt cleaning device (90). In addition, a tension roller (14), a driving roller (15), a secondary transfer backup roller (16), four primary transfer bias rollers (62Y, 62M, 62C, and 62K) are also provided.
The intermediate transfer belt (110) is tensioned by a plurality of rollers including a tension roller (14). Then, it is endlessly moved clockwise in the figure by the rotation of the drive roller (15) driven by a belt drive motor (not shown).
The four primary transfer bias rollers (62Y, 62M, 62C, and 62K) are disposed so as to be in contact with the inner peripheral surface side of the intermediate transfer belt (110), and receive a primary transfer bias from a power source (not shown). Further, the intermediate transfer belt (110) is pressed from the inner peripheral surface thereof toward the photoreceptors (1Y, 1M, 1C, 1K) to form primary transfer nips. In each primary transfer nip, a primary transfer electric field is formed between the photoreceptor (1) and the primary transfer bias roller (62) due to the influence of the primary transfer bias.
The above-described Y toner image formed on the Y photoconductor (1Y) is primarily transferred onto the intermediate transfer belt (110) due to the influence of the primary transfer electric field and nip pressure. On this Y toner image, the M, C, K toner images formed on the photoconductors (1M, 1C, 1K) for M, C, K are sequentially superimposed and primarily transferred. By the primary transfer of the superposition, a four-color superposed toner image (hereinafter referred to as a four-color toner image) that is a multiple toner image is formed on the intermediate transfer belt (110).
The four-color toner image superimposed and transferred onto the intermediate transfer belt (110) is secondarily transferred onto a transfer sheet (not shown) as a recording medium at a secondary transfer nip described later. Transfer residual toner remaining on the surface of the intermediate transfer belt (110) after passing through the secondary transfer nip is cleaned by a belt cleaning device (90) that sandwiches the belt with the driving roller (15) on the left side in the drawing.

Next, the secondary transfer device (22) will be described.
Below the intermediate transfer unit (17) in the figure, a secondary transfer device (22) is provided in which a paper conveying belt (24) is stretched by two stretching rollers (23). The paper conveying belt (24) is moved endlessly in the counterclockwise direction in the drawing in accordance with the rotational drive of at least one of the stretching rollers (23). Of the two stretching rollers (23), one roller disposed on the right side in the drawing is between the intermediate transfer belt (110) and the secondary transfer backup roller (16) of the intermediate transfer unit (17). ) And the paper transport belt (24). By this sandwiching, a secondary transfer nip is formed in which the intermediate transfer belt (110) of the intermediate transfer unit (17) and the paper transport belt (24) of the secondary transfer device (22) are in contact with each other. Then, a secondary transfer bias having a polarity opposite to that of the toner is applied to the one stretching roller (23) by a power source (not shown).
By applying the secondary transfer bias, the four-color toner image on the intermediate transfer belt (110) of the intermediate transfer unit (17) is directed from the belt side to the one stretching roller (23) side in the secondary transfer nip. Thus, a secondary transfer electric field for electrostatic movement is formed. The transfer paper fed into the secondary transfer nip so as to synchronize with the four-color toner image on the intermediate transfer belt (110) by a later-described registration roller pair (49) is affected by the secondary transfer electric field and nip pressure. The received four-color toner image is secondarily transferred. Instead of the secondary transfer method in which the secondary transfer bias is applied to one of the tension rollers (23) as described above, a charger for charging the transfer paper in a non-contact manner may be provided.

  In the paper feeding device (200) provided at the lower part of the copying machine (500) main body, a paper feeding cassette (44) capable of accommodating a plurality of transfer sheets stacked in a bundle of paper is provided in the vertical direction. Are arranged to overlap each other. Each paper feed cassette (44) presses the paper feed roller (42) against the uppermost transfer paper of the paper bundle. Then, by rotating the paper feed roller (42), the uppermost transfer paper is sent out toward the paper feed path (48).

The paper feed path (48) for receiving the transfer paper fed from the paper feed cassette (44) includes a plurality of conveying roller pairs (47) and a pair of registration rollers (near the end of the paper feed path (46)). 49). Then, the transfer paper is conveyed toward the registration roller pair (49). The transfer paper conveyed toward the registration roller pair (49) is sandwiched between the rollers of the registration roller pair (49). On the other hand, in the intermediate transfer unit (17), the four-color toner image formed on the intermediate transfer belt (110) enters the secondary transfer nip as the belt moves endlessly.
The registration roller pair (49) feeds the transfer paper sandwiched between the rollers at a timing at which the transfer paper can be brought into close contact with the four-color toner image at the secondary transfer nip.

  As a result, in the secondary transfer nip, the four-color toner image on the intermediate transfer belt (110) is in close contact with the transfer paper. Then, it is secondarily transferred onto the transfer paper and becomes a full color image on the white transfer paper. The transfer paper on which a full-color image is formed in this manner exits the secondary transfer nip as the paper transport belt (24) moves endlessly, and then is sent from the paper transport belt (24) to the fixing device (25). It is done.

  The fixing device (25) includes a belt unit that moves the fixing belt (26) endlessly while being stretched by two rollers, and a pressure roller (27) that is pressed toward one roller of the belt unit. I have. The fixing belt (26) and the pressure roller (27) are in contact with each other to form a fixing nip, and the transfer paper received from the paper conveying belt (24) is sandwiched between them. Of the two rollers in the belt unit, the roller that is pressed from the pressure roller (27) has a heat source (not shown) inside, and heats the fixing belt (26) by the generated heat. The heated fixing belt (26) heats the transfer paper sandwiched in the fixing nip. The full color image is fixed on the transfer paper by the influence of the heating and the nip pressure.

  The transfer paper subjected to the fixing process in the fixing device (25) is stacked on the stack portion (57) provided outside the left side plate in the drawing of the printer housing, or the toner image is also formed on the other surface. Any of the transport modes is selected to be returned to the secondary transfer nip described above to form the image.

  When a document (not shown) is copied, for example, a bundle of sheet documents is set on the document table (30) of the automatic document feeder (400). However, when the original is a single-sided original that is closed in a main form, it is set on the contact glass (32). Prior to this setting, the automatic document feeder (400) is opened with respect to the copying machine main body, and the contact glass (32) of the scanner (300) is exposed. Thereafter, the single-bound document is pressed by the closed automatic document feeder (400).

  When a copy start switch (not shown) is pressed after the document is set in this way, the document reading operation by the scanner (300) starts. However, when a sheet document is set on the automatic document feeder (400), the automatic document feeder (400) automatically moves the sheet document to the contact glass (32) prior to the document reading operation. In the document reading operation, first, both the first traveling body (33) and the second traveling body (34) start traveling, and light is emitted from a light source provided in the first traveling body (33). The reflected light from the document surface is reflected by a mirror provided in the second traveling body (34), passes through the imaging lens (35), and then enters the reading sensor (36). The reading sensor (36) constructs image information based on the incident light.

  In parallel with such document reading operation, each device in each process cartridge (18Y, 18M, 18C, 18K), intermediate transfer unit (17), secondary transfer device (22), and fixing device (25) are provided. Start driving each one. Then, based on the image information constructed by the reading sensor (36), the optical writing unit (21) is driven and controlled, and toners of the respective colors are provided on the respective photoreceptors (1Y, 1M, 1C, 1K). An image is formed. These toner images become four-color toner images that are superimposed and transferred onto the intermediate transfer belt (110).

  Further, almost simultaneously with the start of the document reading operation, the paper feeding operation is started in the paper feeding device (200). In this paper feed operation, one of the paper feed rollers (42) is selectively rotated, and the transfer paper is sent out from one of the paper feed cassettes (44) accommodated in multiple stages in the paper bank (43). The fed transfer paper is separated one by one by the separation roller (45), enters the reverse feeding path (46), and is then conveyed toward the secondary transfer nip by the conveyance roller pair (47). In some cases, paper feeding from the manual feed tray (51) is performed instead of paper feeding from the paper feeding cassette (44). In this case, after the manual feed roller (50) is selectively rotated and the transfer paper on the manual feed tray (51) is sent out, the separation roller (52) separates the transfer paper one by one and the printer unit (100). Paper is fed to the manual paper feed path (53).

  In the case of forming a multicolor image composed of two or more colors of toner, the copying machine (500) stretches the intermediate transfer belt (110) so that its upper stretched surface is almost horizontal, All the photoreceptors (1Y, 1M, 1C, 1K) are brought into contact with the mounting surface. On the other hand, when forming a monochrome image consisting only of K toner, the intermediate transfer belt (110) is tilted to the lower left in the drawing by a mechanism (not shown), and the upper stretched surface is set to Y, M. , C away from the photoconductors (1Y, 1M, 1C). Of the four photoconductors (1Y, 1M, 1C, 1K), only the K photoconductor 1K is rotated counterclockwise in the drawing to form only the K toner image. At this time, for Y, M, and C, not only the photosensitive member (1) but also the developing device (4) is stopped, and each member of the photosensitive member (1) and the developing device (4) and the developing device ( 4) To prevent unnecessary consumption of the developer inside.

  The copier (500) includes a control unit (not shown) including a CPU that controls each device in the copier (500), an operation display unit (not shown) including a liquid crystal display, various key buttons, and the like. It has. The operator sends a command to the control unit by a key input operation on the operation display unit, so that one of the three modes is selected from the three-sided print mode, which is a mode for forming an image only on one side of the transfer paper. You can choose one. The three single-sided printing modes include a direct discharge mode, a reverse discharge mode, and a reverse decal discharge mode.

  FIG. 2 is an enlarged configuration diagram showing the developing device (4) and the photoconductor (1) provided in each of the four process cartridges (18Y, 18M, 18C, 18K).

  The four process cartridges (18Y, 18M, 18C, 18K) have substantially the same configuration except that the colors of the handled toners are different from each other, and therefore, Y, M, C attached to the developing device (4) in FIG. , K are omitted.

  As shown in FIG. 2, the surface of the photoreceptor (1) is charged by a charging device (not shown) while rotating in the direction of the arrow (G) in the drawing. The surface of the charged photoconductor (1) is supplied with toner from the developing device (4) to the latent image on which an electrostatic latent image is formed by laser light emitted from an exposure device (not shown) to form a toner image. .

  The developing device (4) supplies toner to the latent image on the surface of the photosensitive member (1) while conveying the developer in the direction of arrow (I) in the drawing, and a developing roller (5) as a developer carrying member for developing. have.

The developing roller (5) includes a rotatable developing sleeve (81) and includes a magnet roller (82) as a magnetism generating means that is composed of a plurality of magnetic poles and is rotatable in the direction of the arrow (J) in the figure.
The developing roller (5) can be said to be one of the features of the present invention and will be described in detail later.

  Further, while supplying developer to the developing roller (5), the front side of the paper surface shown in FIG. 2 along the axial direction of the developing roller (5) (hereinafter referred to as the front side in the figure or the front side in FIG. 2 for convenience). In some cases, a supply screw (8) is provided as a supply and conveyance member for conveying the developer toward the case.

  Developer regulating means for regulating the developer supplied to the developing roller (5) to a thickness suitable for development from the portion facing the supply screw (8) of the developing roller (5) downstream in the developer transport direction. The doctor blade (12) is provided.

  The developed developer that has passed through the developing region and separated from the surface of the developing roller (5) on the downstream side in the developer transport direction from the developing region that is the portion of the developing roller (5) facing the photoreceptor (1Y). The collection conveyance path (7) for collecting the toner is opposed to the developing roller (5).

  The collection conveyance path (7) is a spiral arranged parallel to the axial direction as a collection conveyance member for conveying the collected developer collected in the same direction as the supply screw (8) along the axial direction of the developing roller (5). -Shaped recovery screw (6). The supply conveyance path (9) provided with the supply screw (8) is arranged in the lateral direction of the developing roller (5), and the collection conveyance path (7) provided with the collection screw (6) is arranged below the development roller (5). It is installed.

  The developing device (4) is provided with a stirring conveyance path (10) in parallel with the collection conveyance path (7) below the supply conveyance path (9).

  The stirring conveyance path (10) is in the opposite direction to the supply screw (8) while stirring the developer along the axial direction of the developing roller (5). As an agitating and conveying member that conveys toward the back (which may be referred to as the back side in the figure), a spiral agitating screw (11) arranged in parallel to the axial direction is provided.

  The supply conveyance path (9) and the stirring conveyance path (10) are partitioned by a first partition wall (133) as a partition wall. The supply conveyance path (9) and the agitation conveyance path (10) of the first partition wall (133) have openings at the front and back sides in the drawing, and the supply conveyance path (9) and the agitation conveyance path (10). The conveyance path (10) communicates.

  Note that the supply conveyance path (9) and the recovery conveyance path (7) are also partitioned by the first partition wall (133), but the supply conveyance path (9) and the recovery conveyance in the first partition wall (133). An opening is not provided at a place separating the path (7).

  Further, the two developer conveyance paths, ie, the agitation conveyance path (10) and the recovery conveyance path (7), are separated by a second partition wall (134) as a partition member. The second partition wall (134) has an opening on the front side in the figure, and the stirring conveyance path (10) and the collection conveyance path (7) communicate with each other.

  The supply screw (8), the recovery screw (6), and the stirring screw (11), which are developer conveying members, are made of resin or metal screws, each screw diameter is φ22 (mm), and the screw pitch is the supply screw. The two windings of 50 (mm), the collecting screw (6) and the stirring screw (11) are one winding of 25 (mm), and the rotation speeds are all set to about 600 (rpm).

  The developer carried on the developing roller (5) is thinned by a doctor blade (12) made of stainless steel, and is then transported to a developing region that is a portion facing the photoreceptor (1) for development. Is called.

  The diameter of the developing roller (5) is φ25 (mm), and the gap between the doctor blade (12) and the photoreceptor (1) is about 0.3 (mm).

  The developed developer is collected in the collection conveyance path (7), conveyed to the front side in FIG. 2, and stirred and conveyed at the opening of the second partition wall (134) provided in the non-image area. The developer is transferred to the path (10). In the vicinity of the opening of the second partition wall (134) on the upstream side in the developer conveyance direction in the agitation conveyance path (10), on the upper side of the agitation conveyance path (10), as shown in FIG. Toner is supplied from the replenishing port (95) to the agitation transport path (10).

Next, the circulation of the developer in the three developer conveyance paths will be described.
FIG. 3 is a perspective sectional view of the developing device (4) for explaining the flow of the developer in the developer conveying path. Each arrow in the figure indicates the moving direction of the developer.

  4 is a schematic diagram of the flow of the developer in the developing device (4). Like FIG. 3, each arrow in the drawing indicates the direction of movement of the developer.

  In the supply conveyance path (9) that receives the developer from the agitation conveyance path (10), the developer is supplied in contact with the developing roller (5) while moving.

The surplus developer that has moved to the downstream end in the transport direction of the supply transport path (9) without being supplied to the developing roller (5) is fed from the surplus opening (92) of the first partition wall (133) to the stirring transport path (10). ) (Arrow E in FIG. 4).

  On the other hand, the developer supplied to the developing roller (5) is used for development in the developing region, and then separated and separated from the developing roller (5), and is transferred to the collection conveyance path (7). The collected developer transferred from the developing roller (5) to the collection conveyance path (7) and conveyed to the downstream end in the conveyance direction of the collection conveyance path (7) by the collection screw (6) is transferred to the second partition wall (134). It is supplied from the collection opening (93) to the stirring and conveying path (10) (arrow F in FIG. 4).

  In the agitation transport path (10), the excess developer supplied from the supply transport path (9), the recovered developer recovered in the recovery transport path (7), and a toner supply port (95) described later (see FIG. 7). The agitated developer is conveyed to the downstream side of the agitating screw (11) in the conveying direction and to the upstream side of the supplying screw (8) in the conveying direction. It is supplied to the supply conveyance path (9) from the supply opening (91) of the wall (133) (arrow D in FIG. 4).

  A toner concentration sensor (13) (see FIG. 2) composed of a magnetic permeability sensor is provided below the agitation transport path (10), and a toner supply control device (not shown) is operated by the sensor output, and is not shown. Toner is supplied from the toner container.

  The developing device (4) shown in FIG. 4 includes a supply conveyance path (9) and a collection conveyance path (7), and the developer is supplied and collected in different developer conveyance paths. Is not mixed into the supply conveyance path (9). For this reason, it is possible to suppress a decrease in the toner concentration of the developer supplied to the developing roller (5) toward the downstream side of the supply conveyance path (9) in the conveyance direction. Further, since the recovery conveyance path (7) and the agitation conveyance path (10) are provided and the developer recovery and the agitation are performed in different developer conveyance paths, the developed developer does not fall in the middle of the agitation. . Thereby, since the sufficiently stirred developer is supplied to the supply conveyance path (9), it is possible to suppress the developer supplied to the supply conveyance path (9) from being insufficiently stirred. In this way, it is possible to suppress a decrease in the toner concentration of the developer in the supply conveyance path (9), and it is possible to prevent the developer in the supply conveyance path (9) from being insufficiently stirred. The image density can be made constant.

  As shown in FIG. 4, the developer moves from the lower part to the upper part of the developing device (4) only by the arrow (D). The movement of the developer indicated by the arrow (D) is performed by pushing the developer downstream of the stirring conveyance path (10) by the rotation of the stirring screw (11), so that the developer is raised and moved to the supply conveyance path (9). A developer is supplied.

  Such movement of the developer gives stress to the developer and contributes to a decrease in the life of the developer.

  In this way, when the developer is lifted from below to above, the developer is stressed, and the carrier film in the developer is scraped off and the toner is spent at that point, and the stability of the image quality is maintained accordingly. It will disappear.

  Therefore, the life of the developer can be extended by reducing the stress of the developer in the movement of the developer indicated by the arrow (D). By prolonging the life of the developer, it is possible to provide a developing device that suppresses the deterioration of the developer and always has a stable image quality without image density unevenness.

  In the developing device (4) of the present embodiment, as shown in FIG. 2, the supply conveyance path (9) is disposed obliquely above the stirring conveyance path (10). The developer stress in the movement of the developer indicated by the arrow (D) as compared with the case where the supply conveyance path (9) is provided vertically above the stirring conveyance path (10) and the developer is lifted by being disposed obliquely above. Can be reduced.

  Further, in the developing device (4), the supply conveyance path (9) and the agitation conveyance path (10) are arranged obliquely so that the upper wall surface of the agitation conveyance path (10) is supplied and conveyed as shown in FIG. It arrange | positions so that it may become a position higher than the lower wall surface of a path | route (9). In other words, a part of the space constituting the stirring conveyance path (10) has advanced into a part of the space constituting the supply conveyance path (9) in the vertical direction.

  Lifting the supply conveyance path (9) vertically upward with respect to the agitation conveyance path (10) raises the developer against the gravity by the pressure of the agitation screw (11), so that the developer is stressed.

  On the other hand, the developer present at the highest point of the agitation conveyance path (10) is supplied by arranging the upper wall surface of the agitation conveyance path (10) to be higher than the lower wall surface of the supply conveyance path (9). Since it can flow toward the lowest point of the conveyance path (9) without being against gravity, the stress applied to the developer can be reduced.

  In addition, as shown in FIG. 5, the stirring screw (11) in the portion where the stirring and conveying path (10) and the supply and conveying path (9) communicate with each other on the downstream side of the developer conveying path of the stirring and conveying path (10). A fin member may be provided on the shaft. This fin member is a plate-like member composed of a side parallel to the axial direction of the stirring screw (11) and a side perpendicular to the axial direction of the stirring screw. By scooping up the developer with this fin member, it is possible to more efficiently deliver the developer from the stirring conveyance path (10) to the supply conveyance path (9).

  In the developing device (4), the center-to-center distance between the developing roller (5) and the supply transport path (9) is shorter than the center-to-center distance between the developing roller (5) and the stirring transport path (10). In addition, a supply conveyance path (9) and a stirring conveyance path (10) are arranged. Thereby, the developer can be supplied without difficulty from the supply conveyance path (9) to the developing roller (5), and the apparatus can be downsized.

  Further, the stirring screw (11) is rotated in the clockwise direction (in the direction of arrow C in the figure) as viewed from the front side in FIG. 2, and the developer moves the developer along the shape of the stirring screw (11). It is lifted and transferred to the supply conveyance path (9). As a result, the developer can be lifted efficiently, and the stress on the developer can be further reduced.

  FIG. 5 is a cross-sectional explanatory view of the cross section at the rotation center of the supply screw (8) of the developing device (4) as seen from the direction of the arrow (J) in FIG. In the figure, (H) shows a developing region where the developing roller (5) as a developer carrying member supplies toner to the photosensitive member (1) as a latent image carrying member. The width in the axial direction of the rotation axis of the developing roller (5) in the developing area H is the developing area width (α).

  As shown in FIG. 5, the developing device (4) has a supply opening (91) that is a part for lifting the developer from the agitation conveyance path (10) to the supply conveyance path (9), and the agitation from the supply conveyance path (9). A surplus opening (92) for dropping the developer to the transport path (10) is provided in the development area width (α).

FIG. 6 is a schematic diagram of a developer flow in the developing device (4) having a configuration different from that in FIG.
In the developing device (4) shown in FIG. 6, the supply opening (91) and the surplus opening (92) are provided outside the developing region width (α). Since the supply opening (91) is provided outside the development area width (α), the upstream side in the conveyance direction of the supply conveyance path (9) corresponds to the upstream area (β) of the supply conveyance path from the developing roller (5). It is getting longer. Further, since the surplus opening (92) is provided outside the developing region width (α), the downstream side in the transport direction of the supply transport path (9) is the downstream side region (γ of the transport transport path from the developing roller (5). ) It's longer.

  On the other hand, in the developing device (4) having the configuration shown in FIG. 4, the supply opening (91) is provided in the developing region width (α), so the upstream side in the transport direction of the supply transport path (9) It can be shorter than the developing device (4) by the upstream area (β) of the supply conveyance path. Further, since the surplus opening (92) is provided in the developing area width (α), the downstream side in the transport direction of the supply transport path (9) is the downstream area of the supply transport path from the developing device (4) in FIG. It can be shortened by (γ).

  As described above, the developing device (4) in FIG. 4 has the supply opening (91) and the surplus opening (92) in the developing region width (α), so the developing device (4) shown in FIG. Compared to the above, it is possible to save space in the upper part of the developing device (4).

  Next, the position at which toner is supplied to the developer conveyance path including the supply conveyance path (9), the agitation conveyance path (10), and the recovery conveyance path (7) of the developing device (4) will be described. FIG. 7 is an external perspective view of the developing device (4).

  As shown in FIG. 7, the toner replenishing port (95) for replenishing toner is provided above the upstream end in the transport direction of the stirring transport path (10) including the stirring screw (11). Since the toner replenishing port (95) is provided outside the widthwise end of the developing roller (5), it is located outside the developing region width (α).

  The location where the toner replenishing port (95) is provided is on the extended line in the conveyance direction of the supply conveyance path (9), and corresponds to an empty space in the downstream area (γ) of the supply conveyance path in FIG. By providing the toner replenishing port (95) in the empty space by providing the surplus opening (92) within the development area width (α), the developing device (4) can be downsized.

  Further, the toner replenishing port (95) is not limited to the position above the upstream end portion in the transport direction of the stirring transport path (10), but may be provided above the downstream end portion of the collection transport path (7).

Further, a toner replenishing port (95) is provided directly above the collection opening (93) (see FIG. 4) where the developer is transferred from the collection conveyance path (7) to the stirring conveyance path (10). May be.
Since the space directly above the collection opening (93) is also a space that is vacated by providing the surplus opening (92) within the development region width (α), the toner supply port (95) is provided at this position. The development device (4) can be downsized. Furthermore, since the developer is likely to be mixed in the collection opening (93) that is the delivery portion, the developer can be more efficiently stirred by replenishing at this position.

  In the developing device (4) described with reference to FIG. 4, as described above, the developer is supplied from the downstream end in the transport direction of the stirring transport path (10) to the upstream end in the transport direction of the supply transport path (9). An opening (91) and a surplus opening (92) for delivering the developer from the downstream end of the supply conveyance path (9) to the upstream end in the conveyance direction of the stirring conveyance path (10) are within the development region width (α). Therefore, compared to the conventional developing device (4), the space above the developing device (4) can be saved, and the entire developing device (4) can be saved.

  Further, by providing the toner replenishing port (95) in the empty space by providing the surplus opening (92) within the developing region width (α), the developing device (4) can be reduced in size.

  Further, the developer can be efficiently stirred by replenishing the toner from above the recovery opening (93) which is a delivery portion of the developer from the recovery transport path (7) to the stirring transport path (10). .

  Further, by providing the developing device (4) as the developing means of the printer unit (100) of the copying machine as the image forming apparatus, it is possible to save the space of the entire apparatus.

  A toner supply control device (not shown) which is a developer supply means supplies toner in a toner storage portion (not shown) to the developing device (4) from the toner supply port (95). In the developing device (4) of this embodiment, the developer containing toner and carrier is supplied from the toner supply port (95) of the developing device (4). Hereinafter, the developer in which the toner replenished to the developing device (4) and the carrier are mixed is referred to as premix toner. Such a replenishment developer is disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-203814 related to our proposed invention.

  FIG. 8 is a front side end portion of the developing device (4) with the discharge screw (2a), the stirring screw (11), the recovery screw (6), and the doctor blade (12) as discharge discharge members removed. It is a perspective explanatory view of the neighborhood.

  In the developing device (4) of the present embodiment, the circulation conveyance path for conveying the excess developer that has reached the downstream end in the conveyance direction of the supply conveyance path (9) to the upstream end in the conveyance direction of the supply conveyance path (9) is a stirring conveyance path. (10). In addition, the circulating and conveying member that applies a conveying force to the developer in the agitating and conveying path (10) that is the circulating and conveying path is the agitating screw (11). Furthermore, the circulation opening provided near the downstream end in the conveyance direction of the supply conveyance path (9) and through which the passed developer is transferred to the agitation conveyance path (10) which is the circulation conveyance path is the surplus opening (92). . Further, the developing device (4) is provided with a developer discharge port (94) in the supply conveyance path (9) as developer discharging means for discharging the passed developer to the outside of the developing device (4). The developer that has passed through the developer discharge port (94) is delivered as a discharged developer to the discharge conveyance path (2), and the discharge screw (2a) rotates to convey the supply conveyance path (9) in the conveyance direction (FIG. 2). And it is conveyed in the opposite direction (direction toward the back side in FIGS. 2 and 8) from the direction toward the near side in FIG.

  The discharge conveyance path (2) is disposed on the downstream side of the supply conveyance path (9) in the conveyance direction so as to be adjacent to the supply conveyance path (9) with the discharge partition wall (135) interposed therebetween, and the developer discharge port (94). Is an opening provided in the discharge partition wall (135) so as to communicate the supply transfer path (9) and the discharge transfer path (2).

  Further, the developing device (4) reaches the vicinity of the downstream end in the transport direction of the supply transport path (9) and removes the developer that has not entered the surplus opening (92), which is the circulation opening, of the surplus opening (92). A supply downstream end wall surface (80) (see FIGS. 4 and 6) is provided as a developer retaining means for retaining in the vicinity. 4 and 6, the developer discharge port (94), which is a discharge opening, is located above the surplus opening (92) and out of the staying developer retained by the supply downstream end wall surface (80). The developer reaching the position of the developer discharge port (94) is provided to pass therethrough. In other words, the developer that has reached the vicinity of the downstream end in the transport direction of the supply transport path (9) cannot enter the surplus opening (92), and the surplus developer overflowing from the surplus opening (92) is supplied. It is blocked by the downstream end wall surface 80 and becomes a staying developer. When the bulk of the staying developer increases, the developer that has reached the developer discharge port (94) provided above the surplus opening (92) passes through the developer discharge port (94). It is discharged to the discharge conveyance path (2).

  Next, the main part of the developing roller (5), which is a characteristic part of the present embodiment, will be described with reference to FIG.

  The developing roller (5) includes a cylindrical developing sleeve (81) carrying a developer, and a magnet roller (82) as a magnetic field generating means enclosed in the developing sleeve (81) and attracting the developer by magnetic force.

  The developing sleeve (81) is made of a nonmagnetic and conductive material such as aluminum, austenitic stainless steel or magnesium.

  The surface may be smooth, but in a high-speed machine, the following roughening treatment / processing may be performed to suppress developer slip.

(A) Groove extrusion processing such as V-groove or U-groove, machining of various concave shapes, laser processing or edging processing.
(B) Blast processing.
(C) Thermal spraying treatment of metal or ceramic.
The magnet roller (82) is rotatably provided in the arrow (J) direction opposite to the developer conveying direction (P), and an even number of magnets (83) are arranged at equal intervals (shown in FIG. 9). In the configuration of the embodiment, 10 magnets are arranged), and their polarities are opposite to each other so as to attract each other between adjacent magnets.

In the present embodiment, as the driving relationship between the magnet roller (82) and the developing sleeve (81), either the same rotational direction or a relative rotational direction can be selected. 81) is set on the condition that the number of times of opposition between the developer carried on the surface of 81) and the magnet (83) on the magnet roller (82) side increases.

  Due to the increase in the number of times the developer faces the magnet of the magnet roller (82) obtained by setting the drive relationship described above, a spike is formed when the developer is opposed to the magnetic pole, and a spike is formed when the developer is separated from the magnetic pole. The number of repetitions of the phenomenon that the toner is destroyed is increased, and the toner charging characteristics can be improved by increasing the chance of frictional contact between the toner and the carrier.

  In this case, the increase in the number of facings can be obtained by setting the rotational direction of the magnet roller (83) and the developing sleeve (81), setting the speed difference, and the like as described above. That is, when both rotate in the same direction, the number of times the developer faces the magnet (83) can be increased by setting a speed difference between the two, and there is a conflict without setting the speed difference. Similarly, when the direction is set, the number of times the developer faces the magnet (83) can be increased.

  The experimental results based on such a rotational direction or speed difference will be described in Tables 1 and 2.

  As for the above-described magnet (83), a conventional inexpensive ferrite magnet can be used, but a stronger rare earth magnet such as a samarium cobalt magnet or a neodymium magnet can also be used for downsizing and speeding up. . The magnet (83) may be supported on the magnet holder (84) by adhesion, and the outer periphery thereof may be protected with a heat shrink tube or the like (not shown).

If the magnet holder (84) is made of a magnetic material, the magnetic force of the magnet (83) can be slightly improved.
However, since the cost is high and magnetic materials mainly composed of iron are generally high in specific gravity, the moment of inertia increases at the time of high-speed rotation, which may cause a problem in the durability of the drive unit. Therefore, although the magnetic force of the magnet (83) is slightly reduced, nonmagnetic and light specific gravity aluminum or magnesium may be used as a material.

  In FIG. 9, the rotation center (P ′) of the magnet roller (82) and the rotation center (P) of the developing sleeve (81) in this embodiment are not necessarily decentered in the combination with the carrier in this embodiment. The developer peelability can be improved by decentering.

  The direction of eccentricity is set so that the developer carried on the surface of the developing roller (5) can be closest to the inner surface of the developing roller (81) at a position before transferring to the photosensitive member (1). The amount of eccentricity corresponding to the distance indicated by the symbol (T) is an amount that can suppress the carrier from moving to the photosensitive member (1) in the developing region by the magnetic force from the magnetic pole. As a result, the developer transferred to the photosensitive member (1) can be contacted in a state where rising is ensured upon contact with the photosensitive member, and carrier transfer is prevented by the magnetic force from the approaching magnetic pole, so that only the toner is removed. It moves so as to be supplied to the latent image of the photoreceptor.

  On the other hand, the magnetic force can be kept low on the side opposite to the eccentric direction. For this reason, the developer carried on the surface of the developing sleeve 5 can be easily peeled off.

  By providing such an eccentric structure, the developer can be easily peeled off without using external mechanical external force.

  Further, by decentering the magnet roller (82), a gap space (U) is formed between the developing sleeve (81) and the magnet roller (82), and this space (U) corresponds to a magnetic shielding member. A magnetic shield plate (85) is disposed.

  The magnetic shield plate (85) is preferably a ferromagnetic material having a relative magnetic permeability of about 100 to 100,000 and a soft magnetic material having a coercive force of 100 or less, such as iron, silicon steel, permalloy, sendust, ferrite, and amorphous. Can be selected. Furthermore, a material obtained by dispersing the soft magnetic material in a resin material such as polycarbonate, ABS, polystyrene, nylon, etc., and dissolving and molding it can also be used.

  The magnetic shield plate (85) is exposed to the attractive force from the magnet roller (82) due to its magnetic properties. As will be described later, if the suction force is strong and the strength is weak because the two ends are supported, there is a concern that the central portion bends and contacts the magnet roller (82). In order to reduce the attractive force, it is preferable to dispose the magnet sleeve (82) apart from the magnet sleeve (82) within a range not contacting the developing sleeve (81). Further, the thickness of about 0.2 mm to 2 mm can be used, but about 1 mm is preferable from the viewpoint of strength.

By the way, as described above, the magnetic shield plate (85) bends each time it faces the magnetic pole when the magnet roller (82) is rotated, and generates vibration in the so-called longitudinal direction.
Therefore, in the present embodiment, as described above, a configuration in which the contact with the magnet roller (82) due to the bending is avoided and the bending vibration is suppressed is also employed. This configuration will be described later with reference to FIG. I will explain it.

  A configuration in which a magnetic shield member is provided between the developing sleeve and the magnet roller is proposed in, for example, Reference 1 (Japanese Utility Model Laid-Open No. 60-39053).

  However, in this configuration, the main purpose is to select whether or not the magnetic force from the magnet roller is applied to the surface of the developing sleeve.

  Specifically, among the plurality of developing rollers, the magnetic shield member is separated from the developing area so as to be able to act on the developing roller in use, and the above-described case is described in the case of non-use. Contrary to the case, the magnetic shield member is opposed to the developing region so that the magnetic force does not reach.

  For this reason, the rotation of the magnet roller is not performed, and the configuration of the number of times the developer is opposed to the magnetic pole is merely intended to eliminate the spike and the spike of the magnetic brush on the surface in the rotation of the developing sleeve. There is nothing, and there is no idea of facilitating the peeling of the developer in the process of promoting the charging of the toner to the carrier in the developer.

  On the other hand, in a developing device in which the magnet roller does not rotate, it is well known that a repulsive magnetic field is formed by the same polarity by using an odd number of magnetic poles as in the conventional configuration shown in FIGS. And can be easily implemented.

  However, in this embodiment, it is assumed that the magnet roller is rotated, and as described above, unlike the case of using a repulsive magnetic field when an odd number of magnetic poles are provided, FIG. As shown, the number of magnetic poles is an even number. For this reason, the developer cannot be peeled off by forming a repulsive magnetic field with the same polarity when an odd number of magnetic poles are used.

  Therefore, in order to peel off the developer when an even number of magnetic poles are used, a method of peeling off the developer by bringing a flexible scraper into contact with the developing sleeve (81) can be considered. In the embodiment, the magnet roller (82) is eccentric so that the magnetic pole facing the developer peeling position is separated from the inner surface of the developing sleeve (81). Thereby, it is possible to prevent a problem in mechanical durability from occurring as in the case of using a scraper.

  By the way, as configurations in which the developer peeling action is obtained by the difference in the magnetic force, Reference Patent Document 2 (Japanese Patent Laid-Open No. 57-190974) and Reference Patent Document 3 (Japanese Patent Publication No. 04-65379). ).

  However, in order to completely remove the developer using such an eccentric structure of the magnet roller, it is necessary to increase the diameter of the developing sleeve (81) and increase the amount of eccentricity, which may increase the size of the apparatus. is there.

  In the present embodiment, a magnetic shield plate (85) is fixedly disposed in the vicinity of a rotating magnet roller that is eccentric with respect to the developing sleeve so as not to increase the size of the developing sleeve.

  Therefore, unlike the case of combining the above reference patent documents, the repulsive magnetic field for peeling the developer is not formed in the case where the number of times the magnetic pole and the developer are opposed to each other by rotation and the even number of poles is set. However, the present invention is not limited to suppressing the action of magnetic force by eccentricity, but is characterized in that the magnetic attraction of the developer is almost eliminated by providing a magnetic shield plate.

Next, the transfer of the developer in the present embodiment will be described with reference to FIG.
The developer supplied to the developing roller (5) by the supply screw (8) is attracted onto the developing sleeve (81) by the magnetic force of the magnet roller (82) and arranged along the lines of magnetic force. In other words, magnetic spikes are generated on the magnet (83) as indicated by the symbol (B1), and the magnetic spikes fall between the magnets (83) as indicated by the symbol (B2).

  When the rotation direction of the magnet roller (82) is a direction opposite to the rotation direction (I) of the developing sleeve (81) as indicated by a symbol (J), the magnet roller (82) is magnetized while it rotates. The spike rotates in a so-called flip flap shape and proceeds in the direction of arrow (F) opposite to the direction indicated by arrow (J), which is the direction of rotation of the magnet roller (82). At this time, the developing sleeve (81) may be supplementarily rotated in the direction of the arrow (I) at a relatively low speed.

  The developer is controlled to have a constant magnetic head height by the doctor (12), and excess developer is returned to the supply screw (8) in the flow of the arrow (M) and conveyed to the developing roller (5) again while being conveyed in the axial direction. Supplied with.

  As the developer that has passed through the developing doctor (12) continues to rotate, the magnetic roller (82) is gradually decentered to increase the attractive force on the developer sleeve (81), thereby suppressing the carrier from moving to the photosensitive drum. . As the magnet roller (82) rotates at a higher speed, the developer is vigorously agitated at the opposing portion of the photosensitive drum (1), so that the toner can be transferred efficiently according to the latent image.

  As the developer continues to rotate, the attracting force to the developer sleeve (81) gradually decreases due to the eccentricity of the magnet roller (82) and separates from the developer sleeve (81) by its own weight in the supply conveyance path, but remains slightly. Some developer remains in the developing sleeve (81) due to the attracting force.

  Magnetic lines of force generated from the magnet (83) in the vicinity of the magnetic shield plate (85) pass through the magnetic shield plate (85) having a higher magnetic permeability, and there is no leakage magnetic field to the outside of the developing sleeve (81).

  Here, all the remaining developer falls, and the development sleeve (81) completes preparation for the next developer conveyance. As a result, the developer once used for development is not transported as it is toward the development area again, so that the problem that the toner concentration of the developer is lowered can be suppressed.

  By the way, when the width | variety of the magnetic shield board (85), ie, the width along the circumferential direction of a magnet roller (82), is small, the problem that a vibration generate | occur | produces with rotation of a magnet roller (82) is estimated.

  The magnet (83) acting on the magnetic shield plate (85) becomes a single pole, and the magnet (83) is positioned upstream in the rotational direction within the width along the circumferential direction of the magnetic shield plate (85). This is because the direction of the attractive force acting on the magnetic shield plate (85) is switched when it is located on the downstream side in the rotation direction. The vibration propagated to the developing device and became an abnormal image or noise in the form of horizontal stripes.

  Therefore, in the present embodiment, the relationship between the installation angle (R °) corresponding to the width in the circumferential direction of the magnetic shield plate (85) and the arrangement angle (Q °) of the magnetic pole 83 is set to the following relationship. is doing.

R °> Q ° Formula (1)
However, R °: an angle formed by a line connecting each end of the magnetic shield plate (85) in the circumferential direction from the rotation center of the magnet roller (82) Q °: two from the rotation center of the magnet roller (82) The angle formed by the line connecting the centers of the magnets, and thereby the magnetic shield plate (85) always generates an attractive force from the plurality of magnets (83), and the force is averaged to suppress vibration. It was.

  Since this embodiment is configured as described above, the apparatus can be reduced in size. That is, in order to completely remove the developer from the developing sleeve (81) without using the magnetic shield plate, which is a feature of the present invention, as in the operation according to this embodiment, the included magnet roller (82) The amount of eccentricity must be increased to prevent the magnetic force from reaching.

  However, the magnet roller (82) has a limit in reducing the diameter in order to exhibit the function of conveying the developer. Instead, it is necessary to increase the diameter of the developing sleeve (81).

  In this embodiment, the diameter of the magnet roller (83) is about φ17.6 mm. However, when the magnetic shield plate (85) is not provided, the diameter of the developing sleeve (81) needs to be about φ28 to 30 mm. Become.

  On the other hand, when the magnetic shield plate (85) is provided, the diameter of the developing sleeve (81) can be set to φ25 mm, which makes it possible to reduce the size of the developing device. As shown in the figure, in the case of a tandem color laser copying machine, the result is that the entire copying machine can be downsized.

  Next, the configuration in the longitudinal direction of the developing roller (5) used in this embodiment will be described with reference to FIG.

  In FIG. 10, the flange (86) is press-fitted into both ends of the rotatable developing sleeve (81) corresponding to the back side of the image forming apparatus in the lower right, and the developing sleeve (81) and the flange (86) are integrated. Rotation is possible. A bias applying brush (88) is pressed against the flange (86) on the near side to apply a developing bias to the developing sleeve (81).

  A driven gear (89) is fixed to the rear flange (86), and driving is transmitted from a driving gear (not shown) to the developing sleeve (81). Further, supporters 87 are provided at both ends, and the supporter (87) is fixedly supported by the developing device (4).

  Next, the longitudinal cross-sectional structure on the back side of the developing roller (5) used in the present embodiment will be described with reference to FIG. Since the front side cross section has almost the same configuration, the description thereof is omitted.

  In FIG. 11, the outer ring of the ball bearing (91) is press-fitted into the flange (86), and the support sleeve (87) is press-fitted into the inner ring of the ball bearing (91) so that the developing sleeve (81) is rotatably supported. Is done.

On the other hand, the outer rings of the ball bearings (92) and (93) are press-fitted near the center of the supporter (87) to a position eccentric with the ball bearing (91), and the shaft (90) press-fitted into the magnet roller (82) is supported. .
A coupling or gear (not shown) is attached to the tip of the shaft (90) to transmit the drive to the magnet roller. The ball bearings (91) and (92) are shifted in the longitudinal direction to reduce the diameter of the developing roller. The magnetic shield plate (85) is fixedly supported by inserting a pin protruding from a supporter (87) (not shown).

  By the way, in the present embodiment, as described above, it is disposed in the gap space (U) between the magnet roller (67) formed by the eccentricity with respect to the center of the cross section of the developing sleeve (81) and the inner surface of the developing sleeve (81). The magnetic shield plate (85), which is a magnetic shielding member, is flexibly vibrated by repeatedly receiving a magnetic attractive force from the magnet roller (82) side.

Therefore, in the present embodiment, as described above, the magnet roller (8
2) Arrange in a range not in contact with the inner surface, and the occupation range of the magnetic shield plate (85) along the rotation direction of the magnet roller is in the relationship of R °> Q ° as described above in terms of the angle. Is selected.

  However, in the case of a long magnetic shield plate, the span between the supporting positions becomes large and is easily affected by a bending moment, which causes remarkable bending vibration.

  In this embodiment, such a phenomenon can be suppressed, and its configuration will be described below.

  FIG. 12 is a diagram showing an arrangement configuration of the magnetic shield plate (85) with respect to the magnet on the magnet roller (67) side when the vibration suppression measure in this embodiment is not used.

  In the figure, the magnetic shield plate (85) is positioned in a state where the rotational edge of the magnet roller (82) (see FIG. 9) is parallel to the longitudinal direction of the magnet (83) in the longitudinal direction.

  For this reason, as shown in FIG. 12, the magnetic shield plate (85) is in the same state as the beam structure in which both ends are supported, and in the longitudinal direction, the center in the longitudinal direction is most easily deflected by the magnetic attractive force from the magnet side. . This bending and the return to the original shape occur each time the magnets face each other, and vibration is generated by this repetition.

  In this embodiment, the edge along the rotation direction of the magnet roller (82) is formed so as not to be parallel to the magnet (83) on the magnet roller (82) side.

  FIG. 13 shows the magnet (83) of the magnet roller (82) by twisting the edge of the magnetic shield plate (indicated by reference numeral (85 ′) for convenience) along the rotation direction of the magnet roller (82) along the longitudinal direction. The structure which is not parallel to the extending direction of) is shown.

  In this configuration, the period in which the magnetic attractive force from the magnet (83) on the magnet roller (82) side with respect to the edge of the magnetic shield plate (85 ′) acts differs in the longitudinal direction of the magnetic shield plate (85 ′). In other words, the bending deformation cycle of the edge of the magnetic shield plate (85 ′) is different from that in the case where the uniform cycle in the longitudinal direction, in other words, the case in which the suction cycles are matched in the longitudinal direction. . As a result, the bending moment does not occur intensively at the longitudinal center of the magnetic shield plate as in the case where a magnetic attractive force with a uniform period is applied, and the vibration that occurs when the bending moment is concentrated. It is to be suppressed.

  Such a configuration in which the action period of the magnetic attractive force at the edge along the longitudinal direction is different is not limited to twisting the linear edge shown in FIG. 14, but as shown in FIG. It is also possible to form the edge shape into an uneven shape, a sawtooth shape or a zigzag shape. In addition, when the configuration in which the magnetic shield plate (85 ′) supports both ends in the longitudinal direction (longitudinal direction) is targeted, the thickness is varied from the support position side toward the center, specifically, the support position. You may make it raise cross-sectional rigidity so that the side may become thickest.

  In the embodiment described above, the occurrence of flexural vibration due to the magnetic attractive force from the magnet roller (67) is suppressed by devising the shape configuration of the edge portion of the magnetic shield plate (85 ′). The magnetic attractive force itself may be neutralized.

  FIG. 16 shows the configuration in this case. In the figure, a plurality of magnetic poles (indicated by N and S) are provided along the longitudinal direction on the surface of the magnetic shield plate facing the magnet (83) on the magnet roller (82) (see FIG. 9) side. It has been.

  As a configuration in which a plurality of magnetic poles are provided, a configuration in which a magnet sheet (96) is attached to the surface of the magnetic shield plate (85) is employed. The magnet sheet (96) is made of rubber and other elastic materials mixed with ferrite magnets or rare earth magnet powders and molded into a thin sheet. The magnet sheet (96) is affixed to the magnetic shield plate (85) with adhesive tape. To do.

Magnetization is single-sided multipole magnetization (Fig. 16) or double-sided multipole magnetization, etc. The magnetization pitch is about 2 to 8 mm, and the direction of magnetization is parallel to the traveling direction of the magnet (83) to generate vibration. Can be prevented. FIG. 16 shows a state in which the N pole of the magnet (83) faces the magnet sheet (96), while the S pole of the magnet sheet (96) is attracted in the same manner as the configuration shown in FIG. A repulsive force is generated at the pole.
As a result, the force acting on the magnetic shield plate (85) can be reduced by canceling the attractive force and the repulsive force.
As described above, the magnet arrangement on the side of the magnetic shield plate (85) is not limited to arranging a plurality of magnets along the longitudinal direction, but, for example, along the rotation direction of the magnet roller (82). The arrangement may be made as long as the arrangement is such that the magnetic attractive force from the magnet roller (82) side is relaxed and the magnetic shield plate (85) is not deformed.

  By the way, the configuration disclosed in Reference Patent Document 4 (Japanese Patent Application Laid-Open No. 09-211992) is similar to the configuration of the present embodiment, which is similar to the configuration in which the magnetic shield plate (85) is disposed in the gap space (U). is there.

  In this document, as shown in FIG. 20, on the side of the magnet roller (132a) rotating inside the developing sleeve (133) facing the image carrier, the developing sleeve (133) and the magnet roller (132a) The structure which has arrange | positioned the magnetic shielding board (134) in the space between is disclosed.

However, this configuration does not correspond to a configuration in which the magnet roller (132a) is arranged eccentrically with respect to the developing sleeve (133), and the developing sleeve (133) is the same as in References 2 and 3. And the magnet roller (132a) rotate in the same direction.
For this reason, it can be said that the number of times the developer faces the magnet roller when rotating in the same direction is not so many. In particular, in Reference Patent Document 4, since the main purpose is to move the developer in a spiked state toward the development region while remaining in the spiked state, the rotational movement of the developer ( The developer sleeve and the magnet roller are rotated at the same speed because the developer is not moved by rolling), and in such a configuration, the developer and the magnetic pole on the magnet roller side are hardly opposed. I can say no. For this reason, it can be said that there is no idea of increasing the number of oppositions between the developer and the magnet to be obtained in the present embodiment and increasing the chance of frictional contact.

  Accordingly, from Reference Patent Document 4, the effect of increasing the number of frictional contact between the toner and the carrier by increasing the number of times the developer and the magnet roller face the magnetic pole is increased by providing a difference in the rotation speed between the developing sleeve and the magnet roller. It cannot be expected.

  In the embodiment as described above, the developer on the developing sleeve is used even when the magnetic shield plate is simply provided in the space between the developing sleeve and the magnet roller so as not to exert a magnetic force on the surface of the developing sleeve. Since the number of times that the magnetic roller and the magnetic pole on the magnet roller side face each other can be increased, the number of frictional contact between the carrier contained in the developer and the toner can be increased to ensure the toner charge amount. Can be prevented. In addition, even when the even-numbered magnetic pole is provided on the magnet roller and the repulsive magnetic pole is not provided, the developer can be easily peeled off from the developing sleeve. Furthermore, it is possible to obtain a developing device that prevents vibration when the magnetic shield plate used for peeling of the developer is opposed to the magnetic pole of the magnet roller and does not generate noise.

[Two-component developer]
The carrier in the present embodiment has a core material and a coating film that covers the core material, and in the carrier whose surface is covered with the coating film, the coating film contains a binder resin and particles. In addition, the developer layer can be easily peeled off by having a fine concavo-convex structure resulting from particles dispersed in the binder resin on the surface of the clothing layer.
The fine irregularities are 0.01 to 1 μm, preferably 0.01 to 0.07 μm. If the thickness is less than 0.01 μm, no improvement in peelability is observed, and if it exceeds 1 μm, the force with which the particles are restrained is weak. , Long-term peel stability cannot be obtained.

The reason why the developer peeling is improved by the surface irregularities is not clear, but the following reasons are conceivable.
The developer peeling failure is thought to be due to a counter charge generated on the carrier when passing through the developing area, that is, when the toner is consumed, and because the mirror image force acts on the developing sleeve when the agent is peeled off. If it is easy to accumulate, it is considered that a mirror image force acts between the developing sleeve and the developing sleeve when the agent is peeled off, resulting in peeling failure.

In this embodiment, since fine unevenness due to particles is provided on the surface of the resin coating layer, the charge leakage effect due to the protrusion is high, and it is easy to escape the countercharge generated in the carrier when the toner is consumed, so that the mirror image force is difficult to work. It is considered that the developer can be easily peeled off.
In addition, the other reasons are that the contact with the developing sleeve is reduced due to the fine unevenness, and it is difficult to receive electrostatic restraint, and the fluidity of the developer is deteriorated due to the fine unevenness. It can be considered to be strongly influenced by the force necessary for peeling such as gravity and centrifugal force at the time of peeling.

In order to obtain the above effects over a long period of time, the ratio of the average particle diameter of the particles to the average film thickness of the coating film is preferably 0.01 or more and 1.0 or less. Is too small for the film thickness, so it is not enough to create fine irregularities on the surface. If it exceeds 1, the particles will be larger than the film thickness, so the separation of the particles becomes a problem, and image stabilization over a long period of time. Sex cannot be obtained.
The thickness h of the coating layer was determined from the average value by observing the cross section of the carrier using a transmission electron microscope (TEM), measuring the thickness of the resin portion of the coating layer covering the carrier surface.
Specifically, the distance from the carrier cross section to any 50 core material surfaces and the coating layer surface was measured, and the average of the measured values was determined as the thickness h (μm).

  The average particle diameter D of the particles in the coat layer is obtained by adding 300 ml of a toluene solution to 30 ml of aminosilane (SH6020: manufactured by Toray Dow Corning Silicone) in a juicer mixer. Add 6.0 g of the sample, set the mixer rotation speed to low and disperse for 3 minutes. An appropriate amount of the dispersion is added to 500 ml of a toluene solution prepared in advance in a 1000 ml beaker and diluted. The diluting solution is continuously stirred with a homogenizer. The volume average particle diameter is measured with an ultracentrifugal automatic particle size distribution analyzer CAPA-700 (manufactured by Horiba, Ltd.).

Measurement condition rotational speed: 2000 rpm
Maximum particle size: 2.0 μm
Minimum particle size: 0.1 μm
Particle size interval: 0.1 μm
Dispersion medium viscosity: 0.59 mPa · s
Dispersion medium density: 0.87 g / cm ³
Particle density: For the density of inorganic fine particles, the true specific gravity value measured using a dry automatic bulk density meter Accupic 1330 (manufactured by Shimadzu Corporation) is input.

The average height difference of the irregularities on the surface of the carrier of the present invention is preferably 0.02 to 3.0 μm, and at least 0.05 to 2.0 μm. When the average height difference is larger than 3.0 μm, the toner is easily fixed in the concave portion, and the charging performance is likely to be lowered. In addition, the particles forming the convex part may be peeled off and the resistance may be lowered. On the other hand, when the average height difference is smaller than 0.02 μm, the toner scraping effect is reduced, so that the toner is fixed and the charging performance tends to be lowered.
The average unevenness was determined by observing the cross section of the carrier using a transmission electron microscope (TEM) and measuring the thickness of the resin portion of the coating layer covering the carrier surface. Specifically, the distance from the carrier cross section to an arbitrary 50 points of the core surface and the coat layer surface is measured, and the average value of 5 points from the large value of the measured value and the 5 points from the small value of the measured value. The difference from the average was taken.

  When the carrier of the present invention is observed with an SEM, irregularities can be confirmed on the surface, and it can be seen that particles are contained in the coating film. In this case, compared with the case where D / h is larger than 1, the number of convex portions due to particles is reduced, and the average height difference of the unevenness is reduced, but the average film thickness of the coating film is large, so Even during running in the image area, the convex portion is hard to be scraped off, and a decrease in resistance can be suppressed.

  In the carrier of the present invention, the core material is not particularly limited as long as it is a known material, and ferrite, Cu—Zn ferrite, Mn ferrite, Mn—Mg ferrite, Mn—Mg—Sr ferrite, magnetite, iron, nickel, etc. And can be appropriately selected and used according to the use and purpose of use of the carrier. Moreover, it is preferable that the average particle diameter of a core material is 15-100 micrometers. When the average particle diameter is less than 15 μm, carrier adhesion to the electrostatic latent image carrier tends to occur. On the other hand, when the average particle diameter exceeds 100 μm, carrier streaks or the like are generated and the image quality is liable to deteriorate.

The volume resistivity is 1 × 10 ⁹ Ω · cm or more and 1 × 10 ¹⁴ cm or less, preferably 1 × 10 ⁹ Ω · cm or more and 1 × 10 ¹² cm or less. is there.
The volume resistivity of less than 1 × 10 ⁹ Ω · cm, although a good release property, not preferable since thereby also developing carrier during toner development, 1 × 10 ¹⁴ or more, less developer peeling improvement, further edge effect Strongly unfavorable.
As shown in FIG. 21, the volume resistivity is as follows. A cell (31) made of a fluororesin container containing an electrode (32a) and an electrode (32b) having a distance between electrodes of 2 mm and a surface area of 2 × 4 cm is filled with a carrier (33). Using a tapping machine PTM-1 type, a tapping operation is performed for 1 minute at a tapping speed of 30 times / min. A DC voltage of 1000 V is applied between the two electrodes, the DC resistance is measured by a high resistance meter 4329A (4329A + LJK 5HLVLVWDQFH 0HWHU; manufactured by Yokogawa Hewlett-Packard Co., Ltd.), the electric resistivity RΩ · cm is obtained, and LogR is calculated.

Magnetization at a magnetic field of 1kOe is 40 Am ² / kg or more 90 Am ² / kg or less, preferably 60 Am ² / kg or more 90 Am ² / but kg effect by less that is remarkable, in 40 Am ² / kg or less, by pole mug Since the carrier restraining force becomes small, carrier adhesion due to centrifugal force becomes a problem. In particular, in this method in which there are many mag magnetic poles and the magnet rotates, carrier adhesion becomes a problem, which is not preferable. If it is 90 Am ² / kg or more, the force for restraining the carrier at the time of agent peeling increases, and the ghost image deteriorates, which is not preferable.
The magnetic moment can be measured as follows. Using a BH tracer (BHU-60 / manufactured by Riken Denshi Co., Ltd.), 1.0 g of carrier core particles are packed in a cylindrical cell (inner diameter 7 mm, height 10 mm) and set in an apparatus. The magnetic field is gradually increased and changed to 3000 Oersted, then gradually reduced to zero, and then the opposite magnetic field is gradually increased to 3000 Oersted. Further, after gradually reducing the magnetic field to zero, a magnetic field is applied in the same direction as the first. In this way, the BH curve is illustrated, and the magnetic moment of 1000 oersted is calculated from the figure.

The effect is remarkable when the ratio of the weight of the particles to the sum of the weight of the binder resin and the particles is 10% or more and 80% or less, preferably 40% or more and 70% or less.
When the particle content is 10% or less, the carrier coat film is scraped off due to a hazard in the developing unit, and image stability over a long period cannot be obtained. This is because the particles in the coating film also have stability against scraping. On the other hand, if it is 80% or more, there are too many particles relative to the coating resin, so that the force for restraining the particles becomes weak and it is difficult to obtain a stable image.
In addition, the content rate of particle | grains is calculated | required with a following formula.

Particle content (% by weight) = [particles / (particles + total amount of coating resin solids)] Formula (2)

  The developer of the present invention contains the carrier and toner of the present invention. When an image is formed using the developer of the present invention, excellent image quality can be obtained.

  The toner is not particularly limited as long as it is a known toner, and examples thereof include monochrome toner, color toner, and full color toner. The toner contains a binder resin and a colorant, but may be a so-called oilless toner that further contains a release agent. The oilless toner can also be used in a fixing system in which toner fixing prevention oil is not applied to the fixing roll. In general, oilless toners tend to generate so-called spent in which the release agent migrates to the surface of the carrier. However, the carrier of the present invention has excellent spent resistance, and therefore maintains good quality over a long period of time. Can do. In particular, in oilless full color toners, a binder resin having a low glass transition temperature may be used, so that it is generally easy to spend. However, this problem can be solved by using the carrier of the present invention.

  In the developer of the present invention, the toner is preferably a color toner. Since the carrier of the present invention does not contain carbon black in the coating film, the image is not stained with carbon black due to wear or the like. Therefore, it is preferably used for a color developer in which color reproducibility is regarded as important. Examples of the color toner include toners such as yellow, magenta, cyan, red, green, and blue that are used for full color in addition to toners that are generally used in a single color.

  A known resin can be used as the binder resin used in the toner. Specifically, homopolymers of styrene and derivatives thereof such as polystyrene, poly (p-chlorostyrene), polyvinyltoluene, styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers. Polymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-methacrylic acid Acid butyl copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, Styrene-isoprene copolymer, styrene-mer Styrene copolymers such as inester copolymers, polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyester resin, polyurethane resin, epoxy resin, polyvinyl butyral, polyacrylic acid resin Rosin, modified rosin, terpene resin, phenol resin, aliphatic or aromatic hydrocarbon resin, aromatic petroleum resin, or the like can be used alone or in admixture of two or more. As the pressure fixing binder resin, known resins can be mixed and used. Specifically, polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, styrene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer Polymers, ethylene-vinyl chloride copolymers, ethylene-vinyl acetate copolymers, olefin copolymers such as ionomer resins, epoxy resins, polyester resins, styrene-butadiene copolymers, polyvinylpyrrolidone, methyl vinyl ether-maleic anhydride copolymers Polymers, maleic acid-modified phenolic resins, phenol-modified terpene resins and the like can be used alone or in admixture of two or more.

  The colorant used in the toner is not particularly limited as long as it is a known pigment or dye capable of obtaining yellow, magenta, cyan and black toners.

  Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, hansa yellow G, hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake. .

  Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK.

  Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B.

  Examples of purple pigments include fast violet B and methyl violet lake.

  Examples of blue pigments include cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, and indanthrene blue BC.

  Examples of green pigments include chrome green, chromium oxide, pigment green B, and malachite green lake.

  Examples of black pigments include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides.

  These colorants can be used alone or in combination of two or more.

  A known release agent can be used for the toner. Specific examples include polyolefins such as polyethylene and polypropylene, fatty acid metal salts, fatty acid esters, paraffin waxes, amide waxes, polyhydric alcohol waxes, silicone varnishes, carnauba waxes and ester waxes.

  The toner can contain a charge control agent as required. Specifically, nigrosine, an azine dye containing an alkyl group having 2 to 16 carbon atoms (see Japanese Patent Publication No. 42-1627), C.I. I. Basic Yellow 2 (C.I. 41000), C.I. I. Basic Yellow 3, C.I. I. Basic Red 1 (C.I. 45160), C.I. I. Basic Red 9 (C.I. 42500), C.I. I. Basic Violet 1 (C.I. 42535), C.I. I. Basic Violet 3 (C.I. 42555), C.I. I. Basic Violet 10 (C.I. 45170), C.I. I. Basic Violet 14 (C.I. 42510), C.I. I. Basic Blue 1 (C.I. 42025), C.I. I. Basic Blue 3 (C.I. 51005), C.I. I. Basic Blue 5 (C.I. 42140), C.I. I. Basic Blue 7 (C.I. 42595), C.I. I. Basic Blue 9 (C.I. 52015), C.I. I. Basic Blue 24 (C.I. 52030), C.I. I. Basic Blue 25 (C.I. 52025), C.I. I. Basic Blue 26 (C.I. 44045), C.I. I. Basic Green 1 (C.I. 42040), C.I. I. Basic dyes such as Basic Green 4 (C.I. 42000), lake pigments of these basic dyes, C.I. I. Solvent Black 8 (C.I. 26150), quaternary ammonium salts such as benzoylmethylhexadecylammonium chloride, decyltrimethylammonium chloride, dialkyltin compounds such as dibutyl and dioctyl, dialkyltinborate compounds, guanidine derivatives, amino groups Polyamine resins such as vinyl polymers, condensation polymers having amino groups, and metal complex salts of monoazo dyes (Japanese Examined Patent Publication No. 41-20153, Japanese Examined Patent Publication No. 43-27596, Japanese Examined Patent Publication No. 44-6397, and Japanese Examined Patent Publication No. 45- 26478), salicylic acid (see Japanese Patent Publication Nos. 55-42752 and 59-7385), dialkylsalicylic acid, naphthoic acid, dicarboxylic acid zinc, aluminum, cobalt, chromium, iron and other metal complexes Bodies, sulfonated copper phthalocyanine pigments, organic boron salts, quaternary ammonium salts containing fluorine, calixarene compounds, and the like. In color toners other than black, it is not preferable to use a charge control agent that impairs the color, and a white metal salt of a salicylic acid derivative is preferably used.

  An external additive can be added to the toner as needed. As the external additive, inorganic fine particles such as silica, titanium oxide, alumina, silicon carbide, silicon nitride, boron nitride and resin fine particles can be used. By externally adding these to the base toner particles, transferability and durability can be further improved. By covering the surface of the toner with fine particles, it is possible to cover a release agent that lowers transferability and durability, and the contact area is reduced. The surface of these inorganic fine particles is preferably hydrophobized, and metal hydrophobized metal oxide fine particles such as silica and titanium oxide are preferably used.

  As the resin fine particles, polymethyl methacrylate or polystyrene fine particles having an average particle diameter of about 0.05 to 1 μm obtained using a soap-free emulsion polymerization method are suitably used. In addition, the hydrophobized silica and titanium oxide are used in combination, and the amount of added hydrophobized titanium oxide is greater than the amount of hydrophobized silica added. Toner can be obtained.

External additives having a large particle size such as silica having a specific surface area of 20 to 50 m ² / g and resin fine particles having an average particle size of 1/100 to 1/8 of the average particle size of the toner in combination with inorganic fine particles By externally adding to the toner, durability can be improved. This is because the toner is charged by being mixed and stirred with a carrier in the developing device, and the metal oxide fine particles externally added to the toner tend to be embedded in the base toner particles in the process used for development. However, by externally adding an external additive having a particle size larger than those of the metal oxide fine particles to the toner, the metal oxide fine particles are prevented from being embedded. Inorganic fine particles and resin fine particles are contained (internally added) in the toner, but the effect is reduced compared to the case of externally added, but the transferability and durability can be improved, and the pulverization property of the toner is improved. Can be made. In addition, since the external addition and the internal addition are used together, it is possible to suppress embedding of the externally added fine particles, so that excellent transferability can be stably obtained and durability can be improved.

In addition, as a hydrophobizing agent, dimethyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, allyldimethyldichlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, p-chloroethyl Trichlorosilane, chloromethyldimethylchlorosilane, chloromethyltrichlorosilane, p-chlorophenyltrichlorosilane, 3-chloropropyltrichlorosilane, 3-chloropropyltrimethoxysilane, vinyltriethoxysilane, vinylmethoxysilane, vinyltris (β-methoxyethoxy) Silane, γ-methacryloyloxypropyltrimethoxysilane, vinyltriacetoxysilane, divinyldichlorosilane, dimethyl Vinylchlorosilane, octyltrichlorosilane, decyltrichlorosilane, nonyltrichlorosilane, (4-isopropylphenyl) -trichlorosilane, (4-t-butylphenyl) -trichlorosilane, dibenzyldichlorosilane, dihexyldichlorosilane, dioctyldichlorosilane, Dinonyldichlorosilane, didecyldichlorosilane, didodecyldichlorosilane, dihexadecyldichlorosilane, (4-t-butylphenyl) octyldichlorosilane, dioctyldichlorosilane, didecenyldichlorosilane, dinonenyldichlorosilane, di- 2-ethylhexyldichlorosilane, di (3,3′-dimethylbenzyl) dichlorosilane, trihexylchlorosilane, trioctylchlorosilane, tridecylchlorosilane, dioctyl Methyl chlorosilane, octyl dimethyl chlorosilane, 4-isopropylphenyl diethyl chlorosilane, octyltrimethoxysilane, hexamethyldisilazane, hexaethyl disilazane, diethyl tetramethyl disilazane, hexaphenyl disilazane, hexa-tolyl disilazane and the like.
Besides these, titanate coupling agents and aluminum coupling agents can also be used. Further, as an external additive for the purpose of improving the cleaning property, a lubricant such as a metal salt of a fatty acid or polyvinylidene fluoride fine particles can be used in combination.

  As a method for producing the toner, known methods such as a pulverization method and a polymerization method can be used.

In the case of using the pulverization method, the apparatus for kneading the toner includes a batch type two roll, a Banbury mixer, a KTK type twin screw extruder (manufactured by Kobe Steel), and a TEM type twin screw extruder (manufactured by Toshiba Machine). Continuous twin screw extruders such as a twin screw extruder (manufactured by KCK), a PCM type twin screw extruder (manufactured by Ikekai Tekko Co., Ltd.), a KEX type twin screw extruder (manufactured by Kurimoto Iron Works Co., Ltd.), and co-kneader A continuous single-screw kneader such as (manufactured by Buss) is preferably used. The melt-kneaded material obtained using these is cooled and then pulverized. The pulverization can be performed by coarse pulverization using a hammer mill, a rotoplex or the like, and then fine pulverization using a fine pulverizer using a jet stream, a mechanical pulverizer, or the like. The pulverization is preferably performed so that the average particle size is 3 to 15 μm.
Further, the pulverized product is preferably classified using an air classifier or the like so that the average particle diameter is 5 to 20 μm. Next, it is preferable that an external additive is added to the base toner particles. At this time, the base toner particles and the external additive are mixed and stirred using a mixer to coat the toner surface while the external additive is being crushed. The durability can be improved by uniformly and firmly attaching external additives such as inorganic fine particles and resin fine particles to the base toner particles.

EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these. In addition, a part is a weight part.
Using the developing device (4) configured as described above, an experiment was conducted on the number of times the developer faces the magnetic pole using a high-speed copying machine having a continuous print number of 60 to 70 (sheets / minute). The result shown in 2 was obtained.
As shown in FIG. 9, the results shown in Tables 1 and 2 show that the developing sleeve (81) and the magnet roller (83) rotate in opposite directions and the rotation directions are the same. It is important to provide a speed difference.

The structure of the developing device used for the experiment is shown.
(Developer A)
In the conventional developing device, the fixedly arranged magnet roller has 10 magnetic poles. In FIG. 9, the rotation center (P) of the developing sleeve and the center of the magnet mug (P ′) coincide.
Moreover, the magnetic shield plate (85) which is a magnetic shielding member is not provided.
(Developer B)
In the developing device A, the rotation centers (P) and (P ′) were separated by (T), and the magnet mag roller (83) was eccentric.
(Developing device C)
In the developing device B, a magnetic shield plate (85), which is a magnetic shielding member, was installed in a space formed by decentering the magnet mag roller (83).
(Developing device D)
The developing device having the configuration shown in FIG. 19 was used as a target. In the configuration shown in FIG. 19, the magnet roller is fixed.

20 parts by weight of a silicone resin solution SR2410 (manufactured by Toray Dow Corning Silicone), 1 part of aminosilane SH6020 (manufactured by Toray Dow Corning Silicone), conductive particles having an average particle diameter D of 0.02 μm A coating film forming solution was obtained by dispersing 12 parts of carbon black and 300 parts of toluene using a homomixer for 15 minutes. As the core material, a sintered ferrite powder having a weight average particle diameter of 35 μm is used, and a spira coater (manufactured by Okada Seiko Co., Ltd.) is used so that the average film thickness h of the coating film is 0.5 μm. The coating film forming solution was applied to the surface of the core material at 0 ° C. and dried. The obtained carrier was baked in an electric furnace at 300 ° C. for 1 hour. After cooling, it was crushed using a sieve having an aperture of 63 μm, containing 11% by weight of carbon black, D / h of 0.03, average unevenness difference of 0.06 μm, volume resistivity of 10 ¹³ Ω · cm, A carrier having a magnetization of 70 Am ² / kg was obtained. (Details are listed in Tables 1 and 2 below)

  100 parts of polyester resin, 5 parts of C.I. I. Pigment Yellow 180, 2 parts of zinc salicylate and 3 parts of carnauba wax were mixed using a Henschel mixer, and melt-kneaded for 40 minutes at 120 ° C. using two rolls. After cooling, it was coarsely pulverized using a hammer mill and finely pulverized using an air jet pulverizer. The resulting fine powder was classified to produce base toner particles having a weight average particle diameter of 5 μm. Further, 1 part of silica whose surface was hydrophobized and 1 part of titanium oxide whose surface was hydrophobized were added to 100 parts of the base toner particles, and mixed using a Henschel mixer to obtain a toner. A polyester resin having a number average molecular weight of 3800, a weight average molecular weight of 20000, a glass transition temperature of 60 ° C., and a softening point of 122 ° C. was used.

A developer was obtained by mixing and stirring 7 parts of toner and 93 parts of carrier.
The developing device uses the developing device A, and when the magnet roller is rotated at 600 rpm, the developing sleeve can obtain an image density equivalent to that of the conventional example at 300 rpm, and the magnetic pole passes through the path from the supply conveyance path to the collection conveyance path. The number of times was about 15 times.
The evaluation results are shown in Tables 1 and 2 below.

  In Example 1, 1600 parts of a 20% by weight silicone resin solution SR2410 (manufactured by Toray Dow Corning Silicone), 4 parts of aminosilane SH6020 (manufactured by Toray Dow Corning Silicone), 0.15 μm conductive particles. A developer was obtained in the same manner as in Example 1 except that the content was changed to 200 parts of titanium oxide.

  In Example 1, 425 parts of a 20 wt% silicone resin solution SR2410 (manufactured by Toray Dow Corning Silicone), 0.858 parts of aminosilane SH6020 (manufactured by Toray Dow Corning Silicone), 0.35 μm of conductive particles A developer was obtained in the same manner as in Example 1 except that 50 parts of alumina was changed.

  In Example 3, a developer was obtained in the same manner as in Example 3 except that the conductive particles were changed to 170 parts of 0.35 μm alumina.

  A developer was obtained in the same manner as in Example 3 except that the conductive particles were changed to 85.4 parts of 0.35 μm alumina.

  In Example 5, the resin was 118.69 parts of 50% by weight acrylic resin solution Hitaloid 3001, 37.18 parts of 70% by weight guanamine solution Mycoat 106, 0.68 parts of 40% by weight acidic catalyst catalyst. A developer was obtained in the same manner as in Example 5 except for changing to 4040.

  In Example 5, the resin was changed to 51.61 parts of Hitaloid 3001, 16.12 parts of Mycoat 106, 0.28 parts of Catalyst 4040, 241.5 parts of SR2410, 0.55 parts of SH6020. A developer was obtained in the same manner as in Example 5 except that.

  In Example 7, a developer was obtained in the same manner as in Example 7 except that the developing device was changed to B.

  In Example 7, a developer was obtained in the same manner as in Example 7 except that the developing device was changed to C.

  In Example 9, when the magnet roller is rotated at 1200 rpm, the developing sleeve can obtain an image density equivalent to that of the conventional example at 180 rpm, and the number of passes of the magnetic pole in the path from the supply conveyance path to the collection conveyance path is about 30 times. As a result, there was no problem of toner scattering even after changing the developer or after leaving for a long time in a high humidity environment (27 ° C., 80%, 24 hours).

  In Example 9, when the magnet roller was rotated at 2000 rpm, the image density equivalent to that of the conventional example was obtained even if the developing sleeve was fixed, and the number of passes of the magnetic pole in the path from the supply conveyance path to the collection conveyance path was 50 times. Although there was no problem of toner scattering even after leaving the developer and leaving it in a high humidity environment (27 ° C., 80%, 48 hours) for a long period of time, noise of high-speed rotation of the magnet roller was generated.

  In Example 9, when the magnet roller was rotated at 1700 rpm, the developing sleeve had an image density equivalent to that of the conventional example at 300 rpm, and the number of passes of the magnetic pole in the path from the supply conveyance path to the collection conveyance path was 50 times. Although there was no problem of toner scattering even after leaving the developer and leaving it in a high humidity environment (27 ° C., 80%, 48 hours) for a long period of time, noise of high-speed rotation of the magnet roller was generated.

  In Example 9, when the magnet roller was rotated at 400 rpm, the developing sleeve had an image density equivalent to that of the conventional example at 400 rpm, and the number of passes of the magnetic pole in the path from the supply conveyance path to the recovery conveyance path was 10 times. Even after replacement of the developer or after leaving for a long time in a high humidity environment (27 ° C., 80%, 24 hours), there was no problem of toner scattering.

  In Example 9, when the magnet roller was rotated at 1200 rpm, the developing sleeve was rotated in the same direction at 100 rpm to obtain an image density equivalent to that in the conventional example, and in the path from the supply conveyance path to the recovery conveyance path. The number of passes of the magnetic pole was about 40 times, and there was no problem of toner scattering even after changing the developer or leaving it in a high humidity environment for a long time.

  From the above description, it can be seen that there are a plurality of appropriate rotation speed conditions, and these may be set as appropriate. Also, suitable conditions can be set as needed even when the copying speed is different or the developing sleeve diameter is different. The same applies to the rotation direction.

  Further, the above embodiment is a case where the present invention is applied to the developing device having the supply conveyance path, the recovery conveyance path, and the agitation conveyance path in the configuration shown in FIG. The present invention can also be applied to a developing device having only the supply conveyance path and the recovery conveyance path, which is shown in the drawing.

  When applied, the developer that has been sent to the collection transport path is supplied to the supply transport path as it is. It becomes possible to prevent uniformity and density reduction.

In Example 12, a developer was obtained in the same manner as in Example 12 except that non-conductive particles were changed to 200 parts of conductive particles (conductive surface-treated alumina).
Here, the surface treatment layer has a two-layer structure in which tin dioxide is a lower layer and indium oxide containing tin dioxide is an upper layer.

  In Example 12, a developer was obtained in the same manner as in Example 15 except that the particles were changed to 100 parts of conductive particles and 100 parts of nonconductive alumina.

  As a core material, a developer was obtained in the same manner as in Example 12 except that sintered ferrite having a weight-average particle diameter of 35 μm having a low magnetization was used.

  As a core material, a developer was obtained in the same manner as in Example 12 except that sintered ferrite having a high weight average particle diameter of 35 μm was used.

(Comparative Example 1)
In Example 5, a developer was obtained in the same manner as in Example 5 except that the developing device was changed to D.

(Comparative Example 2)
In Comparative Example 1, the addition amount of Hitaloid 3001 was 25 parts, the addition amount of Mycoat 106 was 8 parts, the addition amount of catalyst 4040 was 0.14 parts, the addition amount of SR2410 was 120.5 parts, and the average particle diameter D A developer was obtained in the same manner as in Comparative Example 1 except that the amount of alumina added was 0.3 μm.

(Comparative Example 3)
In Example 7, the carrier has a weight average particle diameter of 19 μm, the addition amount of the hyalloid 3001 is 206.4 parts, the addition amount of the Mycoat 106 is 64.4 parts, the addition amount of SR2410 is 966 parts, and the non-conductive particles are added. A developer was obtained in the same manner as in Comparative Example 1 except that titanium oxide having an average particle diameter D of 0.02 μm was changed and the addition amount was changed to 430 parts.

(Comparative Example 4)
In Comparative Example 1,
Acrylic resin solution (solid content 50% by weight) 56.0 parts Guanamine solution (solid content 77% by weight) 15.6 parts Alumina particles [0.3 μm, specific resistance 1014 (Ω · cm)] 160.0 parts Toluene 900 parts Comparative Example 1 except that 900 parts of butyl cellosolve was dispersed with a homomixer for 10 minutes to prepare a coating film forming solution, coated with a Spira coater (manufactured by Okada Seiko Co., Ltd.) to a film thickness of 0.15 μm, and dried. The developer of the comparative example was obtained in the same manner.

(Comparative Example 5)
In Comparative Example 1,
Acrylic resin solution (solid content 50% by weight) 56.0 parts guanamine solution (solid content 77% by weight) 15.6 parts silicone resin solution SR2410 (20% by weight) 241.5 parts alumina particles [0.3 μm, specific resistance 1014 (Ω · cm)] 900 parts of 88.3 parts toluene was dispersed with a homomixer for 10 minutes to prepare a coating film forming solution, and a Spira coater (manufactured by Okada Seiko Co., Ltd.) was used to obtain a film thickness of 0.55 μm. A developer was obtained in the same manner as in Comparative Example 1 except that it was applied and dried.

(Comparative Example 6)
In Comparative Example 5, a developer was obtained in the same manner as in Comparative Example 5 except that alumina was changed to 258.1 parts and the homomixer was dispersed for 10 minutes.

The evaluation methods and evaluation conditions for each image forming method using each developer are shown below.
The toner scattering margin is determined by printing with an image area of 40% after being left in a high humidity environment for a long period (24 hours) or even longer (48 hours) (27 ° C. and 80%). Conducted a four-step evaluation.
Δ or more was accepted and x was rejected.
For the ghost image, a solid image was printed, and the difference in image density between the end of the sleeve and the circumference of the sleeve was measured by visual observation and ID measurement by X-Rite 938 (manufactured by X-Rite).
0.03 or less was evaluated as “◎”, 0.06 or less as “◯”, 0.1 or less as “Δ”, a value larger than 0.1 as “x”, up to Δ as “pass”, and “x” as “fail”.

For carrier adhesion, after developing the imageless chart with the background potential fixed at 150 V, the number of carriers adhering to the surface of the photoconductor was measured with a loupe, and the average number of carriers adhering per 100 cm ^{2 was} measured. The value was determined. If this value is 20 or less, ◎, 21 to 60 or less, ◯, 61 to 80 or less △, 81 or more to ×, ◎, ○ and △ The test was accepted and x was rejected.

  For the edge effect, a test pattern having a large-area image was output, and the difference between the image density thinness at the center of the obtained image pattern and the image density at the edge was evaluated. No difference is judged as ◎, slight difference is judged as ○, difference is acceptable but △, judgment is unacceptable as ×, ◎, ○ and △ are accepted and x is rejected. It was.

  Regarding the fineness of the image, a character chart having an image area of 5% and a character size of about 2 mm × 2 mm was output to evaluate reproducibility. Those with very good reproducibility are judged as ◎, those with good use as 、, those that can be used practically as △, those that cannot be used practically as ×, ◎, ○ and △ as pass, × as fail did.

  As for durability, 100,000 sheets of a single color were run and the amount of charge reduction and resistance reduction of the carrier after running were evaluated.

  The amount of charge reduction is 95% of the initial carrier mixed with 5 parts of toner and triboelectrically charged, and the toner is removed from the running developer using the blow-off device TB-200 (manufactured by Toshiba Chemical). The difference between the charge amounts Q1 and Q2 (Q1 to Q2) obtained by measuring 95 parts of the carrier obtained by mixing the toner at a ratio of 5 parts of toner and triboelectrically charging the sample using TB-200. The target value is ± 10.0 micro C / g or less. Further, since the cause of the decrease in the charge amount is the spent of toner on the carrier, the decrease in the charge amount can be suppressed by reducing the toner spent.

The amount of resistance change was determined by adding the carrier obtained by removing the toner from the initial carrier and the developer after running using TB-200 between the electrodes of the resistance measurement parallel electrodes each having a gap of 2 mm, and then changing the direct current. The resistance value 30 seconds after applying the voltage 250 V was measured using a high resist meter, and the absolute value of the difference between the values R1 and R2 obtained by converting the obtained resistance value into a volume resistivity (| R1-R2 | The target value is ± 3.0 Ω · cm or less. The causes of resistance change are wear of the carrier coating film, spent toner on the carrier, desorption of particles from the carrier coating film, etc. Can be suppressed.
These results are summarized in Tables 1 and 2.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Discharge conveyance path 2a Discharge screw 4 Developing device 5 Developing roller 6 Collection screw 7 Collection conveyance path 8 Supply screw 9 Supply conveyance path 10 Stirring conveyance path 11 Stirring screw 12 Doctor blade 13 Toner density sensor 14 Stretching roller 15 Drive Roller 16 Secondary transfer backup roller 17 Intermediate transfer unit 18 Process cartridge 20 Image forming unit 21 Optical writing unit 22 Secondary transfer device 23 Tension roller 24 Paper transport belt 25 Fixing device 26 Fixing belt 27 Pressure roller 30 Document base 32 Contact glass 33 First traveling body 34 Second traveling body 35 Imaging lens 36 Reading sensor 42 Paper feed roller 43 Paper bank 44 Paper feed cassette 45 Separating roller 46 Paper feed path 47 Transport roller pair 48 Paper feed path 49 Registration roller pair 50 Manual feed roller 5 Manual feed tray 52 Separating roller 53 Manual feed path 57 Stack portion 62 Primary transfer bias roller 80 Supply downstream end wall surface 81 Developing sleeve 81 Developing roller 82 Magnet roller 83 Magnet 84 Magnet holder 85, 85 'Magnetic shield plate 86 Flange 87 Supporter 88 Bias Applied brush 89 Driven gear 90 Belt cleaning device 90 Shaft (FIG. 11)
91 Supply opening 91 Ball bearing (FIG. 11)
92 Excess opening 92 Ball bearing (Fig. 11)
93 Recovery opening 93 Ball bearing (Fig. 11)
94 Developer discharge port 95 Toner supply port 96 Magnet sheet 100 Printer unit 110 Intermediate transfer belt 133 First partition wall 134 Second partition wall 135 Discharge partition wall 200 Paper feeder 300 Scanner 400 Automatic document feeder 500 Copier α Developing Area width β Supply conveyance path upstream area γ Supply conveyance path downstream area (FIG. 17)
4 Developing device 5 Developing sleeve 401 Developer supplying auger 401P Conveying path 402 Stirring auger (FIG. 18)
4 Developing device 5 Developing sleeve 209 Second auger 401 First auger 401P Agitation chamber 402 Third auger 402P Agitation chamber 403 Partition wall (FIG. 19)
4 Developing device 5 Developing sleeve 401 Supply auger 401P Supply conveyance path 402 Agitation auger 402P Agitation conveyance path 404 Collection auger 404P Collection conveyance path 405 Partition wall 406 Partition wall (FIG. 20)
132a Magnet roller 133 Developing sleeve 134 Magnetic shield plate (FIG. 21)
31 Cell 32a Electrode 32b Electrode 33 Carrier

Japanese Patent No. 3127594 JP 2007-101797 A

Claims (42)

  A developer carrier for supplying a two-component developer containing toner and carrier to the electrostatic latent image formed on the image carrier is provided, and the developer is spiked inside the developer carrier. In an image forming method using a developing device in which a rotatable magnetic field generation means having a magnetic pole to be conveyed is placed, the carrier has a core material and a coating film covering the core material, and the surface Is covered with the coating film, the coating film contains a binder resin and particles, the average height difference is 0.05 μm or more and 2.0 μm or less, and the average film thickness of the coating film is An image forming method using a carrier, wherein the ratio of the average particle diameter of the particles is 0.01 or more and 1.0 or less.   Using the developing device, wherein the magnetic field generating means is arranged with its center in the direction decentered in a direction approaching the image carrier relative to the center of the cross section of the developer carrier. The image forming method according to claim 1.   Due to the eccentricity of the developing device, a part of the magnetic field generating means may be covered with a gap space existing between the side opposite to the image carrier in the magnetic field generator and the inside of the developer carrier. The image forming method according to claim 2, wherein a magnetic shielding member capable of being arranged is disposed.   The image forming method according to claim 1, wherein a ratio of an average particle diameter of the particles to an average film thickness of the carrier coating film is 0.01 or more and 0.7 or less.   The image forming method according to claim 1, wherein the particles in the carrier coating film contain alumina, silica, carbon black, or titanium oxide. 6. The image forming method according to claim 1, wherein the carrier has a volume resistivity of 1 × 10 ⁹ Ω · cm to 1 × 10 ¹⁴ cm. The image forming method according to claim 1, wherein the carrier has a volume resistivity of 1 × 10 ⁹ Ω · cm to 1 × 10 ¹² cm. 8. The image forming method according to claim 1, wherein the carrier has a magnetization in a magnetic field of 1 kOe of 40 Am ² / kg or more and 90 Am ² / kg or less. The image forming method according to claim 1, wherein the carrier has a magnetization of 60 Am ² / kg or more and 90 Am ² / kg or less in a magnetic field of 1 kOe.   The ratio of the weight of the particles to the sum of the weight of the binder resin and the particles of the carrier coating film is 10% or more and 80% or less, according to any one of claims 1 to 9. Image forming method.   The ratio of the weight of the particle to the sum of the weight of the binder resin and the particle of the carrier coating film is 40% or more and 70% or less, according to any one of claims 1 to 10. Image forming method.   12. The image forming method according to claim 1, wherein the magnetic field generating means of the developing device is provided with even-numbered magnetic poles arranged in the rotation direction.   The image forming apparatus according to claim 1, wherein the magnetic shielding member is provided with a shielding angle larger than an angle between magnetic poles provided in the magnetic field generation unit. Method.   14. The magnetic shielding member according to any one of claims 1 to 13, wherein an edge along a rotation direction of the magnetic field generation unit is not parallel to a magnetic pole provided on the magnetic field generation unit. The image forming method described in 1.   The image forming method according to claim 1, wherein the magnetic shielding member is configured by arranging a plurality of magnetic poles along a longitudinal direction of the magnetic field generating unit.   The plurality of magnetic poles provided in the magnetic shielding member have a polarity that can suppress bending vibration along the longitudinal direction of the shielding member due to the magnetic force from the magnetic pole provided in the magnetic field generating means. The image forming method according to claim 1, wherein the image forming method is an image forming method.   The image forming method according to claim 1, wherein a magnetic sheet having a plurality of magnetic poles is attached to the magnetic shielding member.   The image forming method according to claim 1, wherein a plate-like member is used as the magnetic shielding member, and the plate-like member is configured to have a different thickness in the longitudinal direction.   The magnetic shielding member is located closer to the inner side of the developer carrier than the magnetic field generator in a gap space between the surface of the magnetic field generating unit opposite to the side biased to the image carrier and the inner surface of the developer carrier. The image forming method according to claim 1, wherein the image forming methods are arranged close to each other.   20. The magnetic field generating means is rotatable in the same direction or relative direction as the developer carrying member, and when rotating in the same direction, a relative speed difference is set to rotate. The image forming method according to any one of the above.   A developing device comprising a developer carrier for supplying a two-component developer containing toner and carrier to an electrostatic latent image formed on an image carrier, wherein the developer carrier comprises an inside of the developer carrier. Is provided with a rotatable magnetic field generating means having a magnetic pole for conveying the developer in a spike, and the carrier has a core material and a coating film for covering the core material, and the surface thereof The coating film contains a binder resin and particles, the average height difference is 0.05 μm or more and 2.0 μm or less, and the particles with respect to the average film thickness of the coating film The average particle diameter ratio of the developing device is 0.01 or more and 1.0 or less.   Using the developing device, wherein the magnetic field generating means is arranged with its center in the direction decentered in a direction approaching the image carrier relative to the center of the cross section of the developer carrier. The developing device according to claim 21.   A magnetic shield capable of covering a part of the magnetic field generating means in the gap space existing between the opposite side of the magnetic field generating means facing the image carrier and the inside of the developer carrier due to the eccentricity. The developing device according to claim 22, wherein a member is disposed.   The developing device according to any one of claims 21 to 23, wherein the magnetic field generating means is provided with even-numbered magnetic poles arranged along a rotation direction thereof.   25. The developing device according to claim 21, wherein the magnetic shielding member is provided with a shielding angle larger than an angle between magnetic poles provided in the magnetic field generating unit. .   26. The magnetic shielding member according to any one of claims 23 to 25, wherein an edge along the rotation direction of the magnetic field generation means is not parallel to a magnetic pole provided on the magnetic field generation means. The developing device according to 1.   27. The developing device according to claim 23, wherein the magnetic shielding member is configured by arranging a plurality of magnetic poles along a longitudinal direction of the magnetic field generating unit.   The plurality of magnetic poles provided in the magnetic shielding member have a polarity that can suppress bending vibration along the longitudinal direction of the shielding member due to the magnetic force from the magnetic pole provided in the magnetic field generating means. 28. The developing device according to claim 27, wherein:   29. The developing device according to claim 23, wherein a magnetic sheet having a plurality of magnetic poles is attached to the magnetic shielding member.   30. The developing device according to claim 23, wherein a plate-like member is used as the magnetic shielding member, and the plate-like member is configured with different thicknesses in the longitudinal direction.   The magnetic shielding member is located closer to the inner side of the developer carrier than the magnetic field generator in a gap space between the surface of the magnetic field generating unit opposite to the side biased to the image carrier and the inner surface of the developer carrier. The developing device according to any one of claims 23 to 30, wherein the developing devices are arranged close to each other.   32. The magnetic field generating means is rotatable in the same direction or in a relative direction with respect to the developer carrying member, and when rotating in the same direction, a relative speed difference is set to rotate. The developing device according to any one of the above.   33. An image forming apparatus comprising a process cartridge in which at least the developing device according to any one of claims 21 to 32 and an image carrier are accommodated together.   A developer carrier for supplying a two-component developer to the electrostatic latent image formed on the image carrier, and a magnetic pole for carrying the developer in a spiked manner inside the developer carrier A two-component developer mounted on a developing device provided with a rotatable magnetic field generating means, comprising a toner and a carrier, the carrier comprising a core material and a coating covering the core material A coating film, the surface is covered with the coating film, the coating film contains a binder resin and particles, and an average height difference is 0.05 μm or more and 2.0 μm or less; The two-component developer, wherein the ratio of the average particle diameter of the particles to the average film thickness of the coating film is from 0.01 to 1.0.   35. The two-component developer according to claim 34, wherein a ratio of an average particle diameter of the particles to an average film thickness of the carrier coating film is 0.01 or more and 0.7 or less.   36. The two-component developer according to claim 34, wherein the particles in the carrier coating film contain alumina, silica, carbon black, or titanium oxide. 37. The two-component developer according to claim 34, wherein the carrier has a volume resistivity of 1 × 10 ⁹ Ω · cm to 1 × 10 ¹⁴ cm. 38. The two-component developer according to claim 34, wherein the carrier has a volume resistivity of 1 × 10 ⁹ Ω · cm to 1 × 10 ¹² cm. 39. The two-component developer according to claim 34, wherein the carrier has a magnetization in a magnetic field of 1 kOe of 40 Am ² / kg or more and 90 Am ² / kg or less. 40. The two-component developer according to claim 34, wherein the carrier has a magnetization in a magnetic field of 1 kOe of 60 Am ² / kg or more and 90 Am ² / kg or less.   41. The ratio of the weight of the particles to the sum of the weight of the binder resin and the particles of the carrier coating film is 10% or more and 80% or less. Two-component developer.   The ratio of the weight of the particles to the sum of the weight of the binder resin and the particles of the carrier coating film is 40% or more and 70% or less, according to any one of claims 34 to 41. Two-component developer.

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